Cascade virus
From Memory Alpha, the free Star Trek reference.
The devastating effect of this type of computer virus was demonstated in 2373, when the former Starfleet officer Michael Eddington used a virus he had planted before he joined the Maquis to disable the USS Defiant. With the computer's memory erased, the Defiant was completely disabled and had to be towed back to Deep Space 9 by the USS Malinche. He had also placed several similar viruses on Deep Space 9, but Constable Odo managed to remove them. (DS9: "For the Uniform")
