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: 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’, and should not be used interchangeably.