Hack-Back.

Offensive retaliatory action by a private victim against an attacker's infrastructure, generally illegal under most national computer-misuse laws. It belongs to the Defense & Operations category of cybersecurity.

Offensive retaliatory action by a private victim against an attacker's infrastructure, generally illegal under most national computer-misuse laws.

Hack-back, sometimes called active cyber defense outside one's own perimeter, refers to private entities counter-attacking adversary infrastructure to retrieve stolen data, disable a botnet, or destroy malware. In nearly all jurisdictions, including the United States (CFAA), the European Union, and the United Kingdom (Computer Misuse Act 1990), unauthorised access to a third-party system is unlawful — even when that system was used to attack you. Proponents argue hack-back deters attackers and recovers losses; opponents warn of attribution errors, collateral damage to innocent hosts, escalation, and the lack of judicial oversight. Most regulators and frameworks recommend pursuing law-enforcement, takedown providers, and active defense within owned assets instead.

Defences for Hack-Back typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: Counter-hacking, Offensive countermeasures.