Back-hack is the process of identifying attacks on a system and, if possible, identifying the origin of the attacks. Back hacking can be thought of as a kind of reverse engineering of hacking efforts, where security consultants and other professionals try to anticipate attacks and work on adequate responses.
Techopedia explains Back-Hack
In some cases, back hacking can mean tracing an attack to an IP address; in other back hacking efforts, security teams can spot "electronic bread crumbs," or bits of information that an attacker leaves behind. Other efforts at back hacking may be largely pre-emptive, as when security consultants or even rogue coders discover vulnerabilities in a system.
In general, back hacking can raise serious issues within an IT community. Some of the vulnerabilities that these investigators find can compromise vital government or business operations. Back hacking is a fundamental part of finding and deterring threats to cyber-security.