An automated defence routine left in Deep Space 9's computer by the Cardassians to crush a revolt by Bajoran workers, accidentally triggered years later and escalating to a self-destruct countdown.
The counter-insurgency programme is a hidden security system written under Gul Dukat when the station was the ore-processing centre Terok Nor. It appears in the Deep Space Nine episode Civil Defense.
O'Brien and Jake Sisko set it off while clearing old files in the ore-processing unit. Believing the workers have rebelled, the computer seals doors, plays recorded warnings from Dukat, threatens to flood sections with neurocine gas and, as each countermeasure is bypassed, moves to a harsher level. A replicator in Ops produces a disruptor that fires on anyone who is not Cardassian.
The real Dukat beams in to gloat, but when he tries to leave, a further routine added by his superior Legate Kell brands him a coward and starts the self-destruct. Sisko channels the reactor blast into the shields.