Forensics is the art and science of applying computer science to aid the legal process. Linux journal has published a nice introduction to Forensics:
A break-in can happen to any system administrator. Find out how to use Autopsy and Sleuthkit to hit the ground running on your first forensics project.
There are certain aspects to system administration that you can learn only from experience. Computer forensics (among other things the ability to piece together clues from a system to determine how an intruder broke in) can take years or even decades to master. If you have never conducted a forensics analysis on a computer, you might not even know exactly where to start. In this guide, I cover how to use the set of forensics tools in Sleuthkit with its Web front end, Autopsy, to organize your first forensics case.
One of the most common scenarios in which you might want to use forensics tools on a system is the case of a break-in. If your system has been compromised, you must figure out how the attacker broke in so you can patch that security hole. Before you do anything, you need to make an important decision—do you plan to involve law enforcement and prosecute the attacker?