The computer virus was a defense mechanism in the Goldencup Bakery Building's computer system to protect files that could be stolen electronically.
When Coldstone, controlled by the Xanatos Computer Program, attempted to steal defense specifications from the Goldencup Bakery Building's computer system, he was attacked by the computer virus. The computer virus disrupted the Xanatos computer program's control, triggoring the souls of Desdemona and Iago to surface, thowing the cyborg into internal chaos as the three gargoyle souls inside of him struggled for control. When RECAP, operated by Matt Bluestone, attempted to subdue Coldstone, the computer virus was able to download itself into RECAP, via RECAP's taser line.
Goliath used RECAP's virtual reality technology to go inside of Coldstone's mind. There, he saw the computer virus destroying Coldstone's mind. The computer virus consumed Iago and the Xanatos computer program and eventually Othello and Desdemona. The virus then destroyed itself. ("Legion", "High Noon")
The virus still does exist from when it downloaded itself into RECAP and is now in Xanatos's possession, who describes it as the deadliest weapon he knows of. The virus is currently on an isolated system operating on a loop to prevent it from destroying Xanatos's own files or from self-destructing. ("Legion") 
In Coldstone's mind the virus manifested itself as a yellow vortex with pink metallic tentacles that consumed whatever it could grasp.