Computer forensics (sometimes computer forensic science) is a branch of digital forensic science pertaining to legal evidence found in computers and digital storage media. The goal of computer forensics is to examine digital media in a forensically sound manner with the aim of identifying, preserving, recovering, analyzing and presenting facts and opinions about the information.
Although it is most often associated with the investigation of a wide variety of computer crime, computer forensics may also be used in civil proceedings. The discipline involves similar techniques and principles to data recovery, but with additional guidelines and practices designed to create a legal audit trail.
That's what the FBI does....
Anti-computer forensics (sometimes counter forensics) is a general term for a set of techniques used as countermeasures to forensic analysis.
Anti-forensics has only recently been recognized as a legitimate field of study. Within this field of study, numerous definitions of anti-forensics abound. One of the more widely known and accepted definitions comes from Dr. Marc Rogers of Purdue University. Dr. Rogers uses a more traditional “crime scene” approach when defining anti-forensics. “Attempts to negatively affect the existence, amount and/or quality of evidence from a crime scene, or make the analysis and examination of evidence difficult or impossible to conduct.”
It is an approach to criminal hacking that can be summed up like this: Make it hard for them to find you and impossible for them to prove they found you.”
White Hat Hackers help Computer Forensic Specialists by showing how their counter-measures can obfuscate and hide data from forensic examination.
That is what JW does, and it's his specialty.