In June 2024, security researchers published their analysis of a novel implant dubbed “MuddyRot”(aka "BugSleep"). This remote access tool (RAT) gives operators reverse shell and file input/output (I/O) capabilities on a victim’s endpoint using a bespoke command and control (C2) protocol. This blog will demonstrate the practice and methodology of reversing BugSleep’s protocol, writing a functional C2 server, and detecting this traffic with Snort. 

Key findings 

BugSleep implant implements a bespoke C2 protocol over plain TCP sockets. BugSleep operators have demonstrated multiple file-obfuscation techniques to avoid detection. BugSleep implements reverse shell, file I/O, and persistence capabilities on the target system. 

Sending and receiving data 

This blog will use sample b8703744744555ad841f922995cef5dbca11da22565195d05529f5f9095fbfca for analysis. Two of the lowest functions in the C2 stack, referred to as SendSocket (FUN_1400034c0) and ReadSocket (FUN_140003390), are very light wrappers for the send and receive API functions and handle payload encryption. They include some error handling by attempting to send or receive data 10 times before failing.  

This protocol uses a pseudo-TLV (Type Length Value) structure with only two types: integer or string. Integers are sent as little-endian 4- or 8-byte values, and strings are prepended with the 4-byte value of its length. Payloads are then encrypted by subtracting a static value from each byte in the buffer (in this sample it is three).  

Type 

Value 

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