Identifying parasite code characteristics

We just reviewed some common methods for hijacking execution flow. If you can identify where the execution flow points, you can typically identify some or all of the parasite code. In the section Detecting PLT/GOT hooks, we determined the location of the parasite code for the hijacked puts() function by simply locating the PLT/GOT entry that had been modified and seeing where that address pointed to, which, in that case, was to an appended page containing parasite code.

Parasite code can be qualified as code that is unnaturally inserted into the binary; in other words, it wasn't linked in by the actual ELF object linker. With that said, there are several characteristics that can sometimes be attributed to injected code, depending on the techniques used.

Position independent code (PIC) is often used for parasites so that it can be injected into any point of a binary or memory and still execute properly regardless of its position in memory. PIC parasites...