The principle of proactively implementing a spectrum of security measures to strengthen a network or system to make it more robust against attack. Active defence is separate from offensive cyber operations, as well as passive defence or network hardening.
Note that some references to active defence focus on the employment of limited offensive action and counterattacks – commonly referred to as ‘hacking back’. The term active defence is not synonymous with ‘hacking back’, so these terms should not be used interchangeably.