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, passive defence or network hardening. Note that some references to active defence focus on employing 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.