Wednesday, October 30, 2013

FireEye Script To Manage YARA Across An Enterprise

FireEye has been a huge help to cyber security analysts over the years. However, nothing is perfect...and the lack of an API is a huge shortcoming (which I hear they are working on). To compensate for this shortcoming, I've written a bash script that will distribute a file of properly formatted Yara rules (you can also do the same thing for Snort rules) to FireEye devices (even with their latest enforcement of the  rails authenticity token). Enjoy!

Monday, October 28, 2013

XOR From the Unix CLI

Every once in while (depending upon how hard you look) I'm faced with something that looks like an executable, but not quite. A very common tactic used by cyber criminals to evade IDS and analysts is to XOR executables (and sometimes data) so that they don't look suspicious. There are no shortage of ways to XOR, but I thought I'd share an easy method using perl, borrowed from Daniel Wesemann (

In the example below he uses  "cat" and "perl" to perform a single byte XOR (0x77) on a file called "data.hex" and then redirects that to a file called "data.exe". 

cat data.hex | perl -pe 's/(..)/chr(hex($1)^0x77)/ge' > data.exe