This is the third part of the three-part series about code Emulation for Reversing Malware :
Part 1 describes how to use radare2 function emulation along with an exercise of cracking password of function implemented using radare2 python scripting plugin r2pipe.
Part 2 describes how to use the feature to decode a configuration of a Mirai IOT botnet, by implementing the solution in radare python scripting capabilities.
Part 3 improves the script created in the previous by adding more features of searching for addresses of encrypted string and creating function signature to search for decryption function instead of using the hard-coded address of the function.

In the previous two posts we looked at how to emulate a string decryption function call and we created a radare2 macro and python script to use that emulation, we also managed to decrypt some configuration, but not all. In this post we will continue to improve the script, we will continue with the problem finding the address of encrypted data in the previous post and use those address to decrypt the configuration. There another interesting problem I came across when testing this script on the other variant of Mirai samples, the decryption function was not present at the same address as in the previous binary, all thought the function implementation was the same, well I managed to fix that by creating function signature other cool feature of radare. We will also explore many other features improve the script and make it more portable such that if the sample is using the same decryption method then our python script should be able to decrypt the configuration. Let get right into it.

This is the second part of the three-part series about code Emulation for Reversing Malware :
Part 1 describes how to use radare2 function emulation along with an exercise of cracking password of function implemented using radare2 python scripting plugin r2pipe.
Part 2 describes how to use the feature to decode a configuration of a Mirai IOT botnet, by implementing the solution in radare python scripting capabilities.
Part 3 improves the script created in the previous by adding more features of searching for addresses of encrypted string and creating function signature to search for decryption function instead of using the hard-coded address of the function.

In the previous post we looked at how to we can use partial code emulation to decrypt a string in a binary. In this post we will take an example of a popular Linux IOT malware Mirai, the reason for choosing this particular malware is it stores its configuration like CNC server, port etc in encrypted form. Mirai botnet is cross-architecture so for this post we will reverse the x86 architecture version of the binary. The main goal of this post is to automate the configuration decryption using radare2. We will also use radare2 for static analysis of the binary and to reverse a little bit of decryption function.

Yet another Linux Botnet sample by the name of Bushido by a group called 0ffsecurity, but this time things are little interesting, the bad actor is not just interested in using compromised IOT device as DOS attack surface but also using compromised web servers. In this post, we will examine how a small infection shell script which leads to the unravelling of dozens of malware. Solving this case also uncovered the hacker group behind this malware.