Overview
On the night of November 22, 1987, two television stations in Chicago had their signals hijacked by an unknown person wearing a mask of the digital character Max Headroom. The intruder appeared first on WGN-TV and later on WTTW, where they engaged in a 90-second erratic, nonsensical performance.
The Hijacking Process
The perpetrator used a high-powered microwave transmitter to override the stations' links between the studio and the broadcast tower. Despite the technical skill required to perform such a feat, the individual(s) responsible were never caught.
Theories
Numerous theories have circulated for decades, ranging from a disgruntled broadcast engineer to a group of underground pranksters from the Chicago hacker scene. Because signal hijacking is a federal crime, the FBI investigated the case for years without success.