Forensic Analysis of a Live Linux System

During the incident response process we often come across a situation where a compromised system wasn't powered off by a user or administrator. This is a great opportunity to acquire much valuable information, which is irretrievably lost after powering off. I'm referring to things such as: running processes, open TCP/UDP ports, program images which are deleted but still running in main memory, the contents of buffers, queues of connection requests, established connections and modules loaded into part of the virtual memory that is reserved for the Linux kernel. All of this data can help the investigator in offline examination to find forensic evidence. Moreover, when an incident is still relatively new we can recover almost all data used by and activities performed by an intruder.

Sometimes the live procedure described here is the only way to acquire incident data because certain types of malicious code, such as LKM based rootkits, are loaded only to memory and don't modify any file or directory. A similar situation exists in Windows operating systems -- the Code Red worm is a good example of this, where the malicious code was not saved as a file, but was inserted into and then run directory from memory.

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