Iconian software transmission

From Memory Alpha, the free Star Trek reference.

The Iconian software transmission was an information transfer developed by the ancient Iconian civilization. The software uses a small probe that downloads a program into the target's computer system. Once there, the program begins rewriting the software of the destination computer. If the recipient is not Iconian, it begins to cause malfunctions, eventually reaching catastrophic systems failure. The purpose of this transmission was never discovered.

In 2365, the USS Yamato found an abandoned Iconian outpost in the Romulan Neutral Zone and was subsquently infected by the Iconian probe. The Yamato was later destroyed by the program when it caused an uncontrolled release of antimatter into the Yamato's warp core. The program spread to the USS Enterprise-D and the IRW Haakona when they downloaded the Yamato's logs. Enterprise Chief Engineer Geordi La Forge discovered that the program could be purged by shutting down all ship systems, erasing the infected areas, and then rebooting from the computer core's protected memory. This technique was discovered when Commander Data, an Android who had also been infected by the program, appeared to die, but awakened moments later, having restored his programming to normal. (TNG: "Contagion")