The field of computer forensics is widespread and includes many facets of investigation. One such facet is the analysis of executable code. One of the most insidious places for a hacker to install some type of malicious functionality is within an executable file of some kind. In Linux, this is, of course, the ELF file type. We already explored some of the infection techniques that are being used in Chapter 4, ELF Virus Technology – Linux/Unix Viruses, but have spent very little time discussing the analysis phase. How exactly should an investigator go about exploring a binary for anomalies or code infections? That is what this chapter is all about.
The motives for an attacker infecting an executable varies greatly, and it may be for a virus, a botnet, or a backdoor. There are, of course, many cases where an individual wants to patch or modify a binary to achieve totally different ends such as binary protection, code patching, or other experimentation...