A brain-melting computer virus was featured prominently in the episode "The No-Brainer".
The virus downloads itself to a computer through the internet. Targets can be selected by the creator of the virus as well. The virus first manifests itself in the form of a pop-up window, with the question "What's that noise?" prompting the user to click a link. Clicking the link executes the virus, which is simply a video of strange, seemingly unrelated and distorted clips of many things, including a hand, a lighthouse, and the side of a building. Viewers are often entranced by the images and are unable to look away; some even experience the hallucination of their computer screen stretching into a hand and grabbing their head. These images, mixed with high-frequency audio, cause the viewer's brain to liquefy and exit through any available orifices, most commonly the mouth, nose, and ears. The virus also irreparably damages the computer's hard drive, fusing it together.
The virus was created by Brian Dempsey, a disturbed man who had been left by his wife, Miriam, and fired by his boss, Paul Wiles. Vengeful, Dempsey went into seclusion and began designing a computer virus that, when viewed, would cause the viewer's brain to liquefy.
Dempsey then proceeded to send the virus to Paul Wiles' son, Gregory Wiles, who unsuspectingly watched the video and was killed after experiencing its terrible effects. Dempsey also sent the virus to the general manager of a car dealership, presumably for bad business between the two. The virus was also sent to Mark Rosenthal, his ex-wife Miriam's new husband, which caused Mark's death. The virus also began downloading on Olivia Dunham's laptop after she began investigating him, and nearly took the life of Olivia's niece Ella Blake, though Dempsey, who saw that the user was a child through the laptop's webcam, remotely deactivated the program before it killed her.
Dempsey was soon discovered by the FBI, however, though he committed suicide with a concealed handgun before they could apprehend him. The virus was presumably destroyed or contained by the FBI afterward. ("The No-Brainer")