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Codegate 2011 CTF – Binary200 – Anti Debugging Techniques Explained


Again I stumbled upon a nice reverse-me, binary200 from the Codegate 2011 CTF.
And again there are some really interesting anti-debugging tricks implemented, so I decided to produce another video.
The instruction was just "reverse me", which means there should be a key or a flag somewhere in that binary, right?

Let’s check it out………….

Thanks to Codegate and to the creators of the CTF for such a nice challenge!
CODEGATE is an annual IT Security Festival in Seoul since 2008 and it is already one of the biggest IT security events.


Notes :

  • My system was a Windows XP SP3 box. So the addresses here may be different to the addresses of your box
  • I named the binary a2.exe
  • Always use a virtual machine when you reverse a unknown binary (you’ll see in a minute why)
  • At the time of producing this video the binary was available here: / /


Video :

You can view a full screen version here, and you can download the movie here.




Anti-Debugging techniques:

  1. TLS callback:  !bpxep -tls
    Debugging options –> Make first pause at: –> System breakpoint
  2. Check from PEB if Debugger is attached
  3. PEB!NtGlobalFlags
  4. NtQueryInformationProcess
  5. Create new SEH followed by the int 2D anti-debugging technique

Date check

Checking of the current date: the current date should be Sat Feb 26 2005




© 2011, Corelan Team (fancy). All rights reserved.

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