Vighnesh Raje

Often there comes a scenario where a malware has run on the host system and there is suspicion of data exfiltration. One forensic technique that comes in handy in such situations is SRUM forensics. Introduction to System Resource Usage Monitor SRUM was first introduced in Windows 8 operating system for keeping a track of system resource usage. In particular, information such as process owner, CPU cycles used by the process, data bytes read/written, network data sent/received, Windows push notifications and energy usage is continuously recorded. SRUM is part of diagnostic policy service and it monitors desktop applications, programs, services, windows applications and network connections. The data that is visualized when one open’s the task manager is part of SRUM data feed. The SRUM data collection happens once in every hour and at shut down. SRUM uses the below extensions for monitoring and data collection. Source: Windows 8 SRUM Forensics - SANS DFIR Summit 2015(Slides) b

    PlugX a Remote Access Trojan (RAT) was first identified in 2012. PlugX is known to be used against high profile government institutions and other organizations and has evolved since then. PlugX has also been seen as Korplug, SOGU and DestroyRAT. The primary functionality of this malware is to:      Provide persistence access for adversaries.    Perform surveillance of the infected machines.      Reach out to a command and control server.      Hijack legitimate executable and inject malicious code. Since the identification of PlugX in 2012, it has mutated in complexity and exploitation techniques. PlugX is commonly seen to be used in advanced targeted attacks, with capabilities to impersonate authentic processes and perform extensive recon on infected machines. The malware sample analyzed in this blog, has been downloaded from the internet. Basic Static Analysis The malware sample analyzed in this blog is a 32-bit Executable, having a compiler timestamp of Feb 10, 2010.

  Let’s begin with the main function. So firstly, the string “Reversing.Kr Easy ELF\n\n” defined in the .data section is printed to stdout. Further, we can see two function calls – sub_8048434 and sub_8048451. Finally, the return value of function sub_8048451 is checked. If the return value is false, string “Wrong\n” is printed to stdout. Let’s now proceed to check function sub_8048434. This function reads an input of type string and stores it at address starting from 0x804A020 using “scanf”. As a test scenario let’s consider our input is “xxxxxxx”. Moving ahead to function sub_8048451. Here we have a series of checks in place. If all the checks are passed, the function returns true or else false. So now let’s analyze each check individually. In the first case, the 2nd byte of the input is checked to verify weather it is “1”. So now we know, the correct key should be something like “x1xxx..”   Then, in the second case, its checks if the 5 th byte of the input is “X”. M