A computer virus is a program designed to co-opt, hamper, or damage the functionality of a computer.
History[]
When the Wraith attacked Atlantis, Dr. Radek Zelenka designed a computer virus to upload to the Atlantis database in order to keep the Wraith from accessing the information. (SGA: "The Siege, Part 2")
When Major General Henry Landry released Nerus, he ordered Dr. Bill Lee to plant a computer virus in his devices in order to disable the shield of Ba'al's Ha'tak. (SG1: "Off the Grid")
When a group of Wraith tried to ally themselves with Atlantis, they downloaded a virus with the information they shared. They were able to steal the location of Earth and a means to improve their hyperdrive before the virus deleted the information. (SGA: "Allies")