Computer virus
From Memory Alpha, the free Star Trek reference.
A computer virus is a self-replicating program, usually designed with the intention of causing damage to or otherwise altering computer systems. The nomenclature originates from a pathological virus in the sense that a virus reproduces and causes harm to its host.
In 2154, the warp matrix of the Enterprise was compromised by a subroutine planted by a group of Klingon Augments. The subroutine also compromised the starship's command protocols. (ENT: "Affliction", "Divergence")
The Iconian software transmission was originally thought to have been a computer virus when the USS Enterprise-D encountered it in 2365. (TNG: "Contagion")
Prior to his open defection to the Maquis in 2372, Michael Eddington planted cascade viruses in Deep Space 9 and the USS Defiant's computers. This allowed him to disable the Defiant at a critical time. (DS9: "For the Uniform")
Ramuran tracers use computer viruses to eliminate any records of their presence from alien ships. Both of USS Voyager's encounters with the Ramurans in 2374 were erased in this manner. (VOY: "Unforgettable")
