Thirty years ago today, a person or persons unknown briefly hijacked the signal of two Chicago television stations, broadcasting a bizarre taped message from a man wearing a Max Headroom mask. The "broadcast intrusion" interrupted a primetime news broadcast from Chicago's WGN, and then (more successfully) the 11:00pm broadcast of Dr. Who on the Chicago public television station WTTW. To this day, the perpetrators of the television hack remain unknown.

The hack was made possible by the analog television broadcast technology of the day—the attacker was able to overpower the signals sent by the television studios to a broadcast antenna atop the John Hancock building in Chicago with his or her own signals. In the case of the WGN news broadcast, engineers were able to change the frequency used in the uplink to the John Hancock tower after a brief interruption, and the audio from the pirate transmission was drowned in static. But the WTTW takeover lasted a full 90 seconds, and the pirate TV broadcast's audio, while distorted, was audible to anyone who happened to be tuned in.

Broadcast intrusions were not rare in the 1980s. The first major one took place in 1977, when someone interrupted the audio of an ITV Southern Television broadcast from a tower in Hannington, England, with a message purported to be from an alien representative of an "Intergalactic Association." The message warned, "All your weapons of evil must be removed… You have but a short time to learn to live together in peace."

As with the Chicago takeover, the Hannington broadcast tower was connected by a wireless uplink, not a hard-wired connection. And in 1986, supporters of the Polish labor movement Solidarność hijacked state television stations with printed anti-government messages. State television stations across the Soviet Union were frequently taken over by pirate transmissions that overpowered transmissions from relay stations.

But the Max Headroom broadcast was both more comical and creepy. The man in the Max Headroom mask called out a WGN commentator, Chuck Swirsky, whom he referred to as a "frickin' liberal." He also spoofed a Coca-Cola advertising campaign featuring Max Headroom, saying "catch the wave" (Coke's slogan) while holding up a Pepsi can—then crushed the can and tossed it, holding up a middle finger with a rubber extension.

After a bizarre homage to the 1959 pseudo-animated television series Clutch Cargo and complaints about "my piles" (or maybe "my files"), he declared he had "made a giant masterpiece for all the greatest world newspaper nerds"—a reference to the Tribune Company and WGN's call sign, which was intended to be an acronym for "World's Greatest Newspaper." He then exposed his buttocks, crying "they're coming to get me!" and then moaning as a woman spanked him with a flyswatter.

The end of analog television broadcasting in the US and the conversion to digital signals—as well as the increased use of cryptography to secure wireless data links—has made broadcast intrusions much more difficult, but not impossible. The HDTV broadcast of a Washington DC ABC affiliate was hijacked in 2007, with a morning news broadcast being superimposed with a black and white photo of a man and woman.

Radio stations are still vulnerable to this sort of attack however, because FM and AM stations still rely largely on analog. A local radio station in Mansfield, England, had its signal hijacked by someone in July eight times—overriding broadcasts with "The Winker's Song" by a comedy band called Ivor Biggun. And a radio attack in April caused tornado sirens in Dallas to sound at midnight.