Forensic analysis of a Linux disk image is often part of incident response to determine if a breach has occurred. Linux forensics is a different and fascinating world compared to Microsoft Windows forensics. In this article, I will analyze a disk image from a potentially compromised Linux system in order to determine the who, what, when, where, why, and how of the incident and create event and filesystem timelines. Finally, I will extract artifacts of interest from the disk image.
In this tutorial, we will use some new tools and some old tools in creative, new ways to perform a forensic analysis of a disk image.
The scenarioPremiere Fabrication Engineering (PFE) suspects there has been an incident or compromise involving the company's main server named pfe1. They believe the server may have been involved in an incident and may have been compromised sometime between the first of March and the last of March. They have engaged my services as a forensic examiner to investigate if the server was compromised and involved in an incident. The investigation will determine the who, what, when, where, why, and how behind the possible compromise. Additionally, PFE has requested my recommendations for further security measures for their servers.
The disk image
To conduct the forensic analysis of the server, I ask PFE to send me a forensic disk image of pfe1 on a USB drive. They agree and say, "the USB is in the mail." The USB drive arrives, and I start to examine its contents. To conduct the forensic analysis, I use a virtual machine (VM) running the SANS SIFT distribution. The SIFT Workstation is a group of free and open source incident response and forensic tools designed to perform detailed digital forensic examinations in a variety of