PvIB Pen.Testing workshop

2015-10-07 06:32:00

The CTF site

Last night I attended PvIB's annual pen-testing event with a number of friends and colleagues. First impressions? It's time for me to enroll as member of PvIB because their work is well worth it!

In preparation to the event I prepared a minimalistic notebook computer with a Windows 8 and Kali Linux dual-boot. Why Kali? Because it's a light-weight and cross-hardware Linux installer that's chock-full of security tools! Just about anything I might need was pre-installed and anything else was an apt-get away. 

Traveling to the event I expected to do some networking, meeting a lot of new people by doing the rounds a bit while trying to pick up tidbits from the table coaches going around the room. Instead, I found myself engrossed in a wonderfully prepared CTF competition. In this case, we weren't running around the conference hall, trying to capture each other's flags :D The screenshot above shows how things worked:

  1. Each participant would register an account on fragzone.nl
  2. Your personal dashboard showed the available challenges, each worth a number of points.
  3. Supposedly easy challenges would net you 50-100 points, while big ones would net 250, 500 or even 1000!
  4. Each challenge would result in a file or piece of text, which one needed to MD5 and then submit through the dashboard.

I had no illusions of my skillset, so I went into the evening to have fun, to learn and to meet new folks. I completely forgot to network, so instead I hung out with a great group of students from HS Leiden, all of whom ended up really high in the rankings. While I was poking around 50-200 point challenges, they were diving deeply into virtual machine images searching for hidden rootkits and other such hardcore stuff. It was great listening to their banter and their back-and-forth with the table coach, trying to figure out what the heck they were up to :)

I ended up in 49th place out of 85 participants with 625 points. That's mostly middle of the pack, while the top 16 scored over 1400 (#1 took 3100!!) and the top 32 scoring over 875. 

Challenges that I managed to tackle included:

Together with Cynthia from HSL, we also tried to figure out:

The latter was a wonderful test and we almost had it! Using various clues from the web, which involved multiple steganography tools provided by Alan Eliason, ImageMagick and VLC. We assumed it was a motion-jpeg image with differences in the three frames detected, but that wasn't it. Turns out it -was- in fact steganography using steghide.

Ironically the very first test proved very annoying to me, as the MD5 sum of the string I found kept being rejected. It wasn't until our coach hinted at ending NULL characters that I switched from "cat $FILE | md5sum" to "echo -n $STRING | md5sum". And that's what made it work. 

To sum things up: was I doing any pen-testing? No. Did I learn new things? Absolutely! Did I have a lot of fun? Damn right! :)

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