A couple of times in the past I have blogged about numbers stations, a slightly creepy phenomenon where coded messages are broadcast over shortwave radio frequencies.

But more recently I have become interested in a similar phenomenon which is almost the reverse of numbers stations. Whereas numbers stations are seemingly utilised by the state for spying activities, broadcast signal intrusion is usually the opposite — members of the public hijacking television and radio broadcasts.

Perhaps the most well known is a pirate who posed as Max Headroom, hijacking two broadcasts in Chicago in 1987. The perplexing thing about it is that the broadcast was so cryptic — if it had a meaning at all, that is — that most people just scratch their heads wondering about the imposter’s motive.

The first successful hijack was short lived. It interrupted the evening news bulletin on WGN. However, only the images came through, and no audio was broadcast. An engineer at the transmitter site was able to re-gain control within 30 seconds.

Reports say that the pirate attempted to hijack several other broadcasts in Chicago, but none of them were successful. But two hours later the imposter successfully interrupted an episode of Doctor Who that was being broadcast on WTTW. No engineer was present at the transmitter, so the pirate broadcast carried on until its end. It lasted only 90 seconds, but it could have been much longer.

If numbers stations didn’t send shivers up your spine, surely this would. Imagine sitting there watching television as normal, only to be faced with this creepy transmission.

The video fascinates me. First of all, as I have mentioned, the motives are unclear. There is a cryptic message about “the greatest world newspaper nerds”. WGN, the first station to be hijacked, stands for World’s Greatest Newspaper. This suggests that WGN was the real target, but with the attempt having misfired the imposter went on to find any old place to broadcast his odd — at points disturbing — message. Even if you reach the conclusion that the message was aimed at WGN, what that message actually was is a complete mystery.

Some speculate that whoever was behind the video was simply drunk or high. I doubt this is the case. The broadcast was clearly pre-meditated. It is obvious that the message was pre-recorded because it went out twice, and there are continuity errors when the shot changes towards the end of the broadcast.

There are also probably at least three people involved in the making of the broadcast. There are at least two actors, and two people would probably be required to rotate the sheet of corrugated metal that’s used as the backdrop (the rotation is not CGI or mechanical because it is inconsistent).

A lot of technical equipment may be involved as well. Immediately after the hijacking, authorities claimed that a transmitter powerful enough to hijack a television broadcast would cost as much as $600,000 to buy, or several thousand dollars to rent. However, it seems as though this was misinformation designed to dissuade copycats.

Nevertheless, it is clearly at least a semi-professional job. Even putting aside the equipment needed to overpower a television broadcast signal, the quality of the recording looks really good for 1987 standards and the distortion in the vocals suggests at least a modicum of expertise. It obviously wasn’t amateur stuff.

Yet, the message and motive is difficult to decipher. YouTube contains another video containing subtitles with a likely transcript of what the imposter dressed as Max Headroom was saying. If you’re interested enough, I’d also skim through the comments which have interesting additional suggestions. (The subtitles in the YouTube video are definitely wrong in parts.)

Over twenty years on, people are still unclear about the intentions behind the pirate broadcast. It was clearly designed to be ambiguous. But it clearly took considerable time and effort to pull it off. No-one has ever come forward to admit to the pirate broadcasts.

Perhaps the person did it just for fun — a precursor to the hacker culture that became more prevalent in the 1990s. Perhaps it was social commentary. After all, the original Max Headroom programmes were set in a future dystopia where the world was run by giant television corporations and freedom fighters utilised exactly this trick of interrupting regular broadcasts.

The theory I favour holds that the person was a former employee of WGN who had been fired — not by his boss, but by an underling (hence the line “be a man”). This was his form of revenge.

There is a brilliant article about the Max Headroom pirating incident at Damn Interesting.

The fake Max Headroom remains at large, but another (less sophisticated) hijack broadcaster was caught. This simple broadcast is less intriguing than the Max Headroom incident in terms of its message, but is interesting because it is a successful hijacking of a satellite transmission.

A person calling himself Captain Midnight hijacked an HBO broadcast with a simple caption complaining about the channel’s price. The caption also contained an ominous threat, seemingly implying that broadcasts on two other channels would also be hijacked.

It transpired that Captain Midnight was John MacDougall, a satellite television dealer who felt that HBO’s then new fangled subscription model was hurting his sales. He was caught when a member of the public overheard him bragging about it.

Less well-known, but perhaps the scariest hijack broadcast of them all, happened in the UK way back in 1977. This seems to be among the very first examples of hijacking a broadcast, and is perhaps the most impressive. Unlike the Max Headroom incident, the motive here was clear, the message was relatively unambiguous and the broadcast was a complete success.

During an ITN news bulletin broadcast on Southern Television, the audio started crackling and the newsreader’s voice was replaced by that of “Vrillon of the Ashtar Galactic Command”. The pictures of the news broadcast continued uninterrupted. But the sound of the news was replaced by an ‘alien’ warning of an imminent global disaster unless humans became peaceful and dismantled their weapons.

Here is a great video — the audio is genuine but the pictures are not. Carry on until the end to hear follow-up news reports on the incident.

Vrillon of the Ashtar Galactic Command Incident from Labyrinth13 on Vimeo.

An impressive feat. The audio is very crackly in moments, but this is a successful hijacking of a broadcast to disseminate a clear message. Like the Max Headroom incident, a lot of planning appeared to go into it, with a series of electronic effects designed to make it sound like an alien broadcast, and samples of Looney Tunes cartoons.

Once again, the imposters have never come forward. However, given the message that put out and the irreverent set-up, it seems likely that it was a group of students who had some technical know-how and access to decent equipment.

It was rather naughty though, and clearly very distressing for some viewers. I suppose I would be too. What I would do is switch the channel to make sure I wasn’t going mad or that aliens actually were talking to me. However, these imposters successfully hijacked five major terrestrial transmitters. This is concerning, because it means that these people could feasibly have hijacked every television channel in one area and then some.

These successful hijacks are really disturbing. Apparently it is easy to hijack an analogue television signal. The only reason we haven’t seen more of it is simply because people haven’t found out about it.

Although there are only a few well-known instances of broadcast intrusion in the western world, they are much more common in less free countries. Falun Gong use the technique in China. And according to Wikipedia they were a regular feature of television in the Soviet Union.

In the mid-1980s one of Poland’s leading astronomers, Jan Hanasz, managed to superimpose captions on top of state television broadcasts. Using basic equipment, he and three others managed to display the logo of the Solidarność labour movement and implored viewers to boycott elections. Some say this action was one of the first cracks in the Iron Curtain.

That is an example of using this technique for good. But imagine if there was a genuine major national emergency. Any rogue elements with enough know-how and resources could easily hijack the emergency transmissions to spread misinformation or generally wreak havoc and cause panic.

A part of me wonders if this is the real reason why governments around the world are in the process of switching off analogue transmissions and engaging in a digital switchover process. Digital broadcast signals are encrypted, making them much more difficult to hijack.

But pranksters are using different methods to hijack digital broadcasts. Some Czech artists are currently standing trial after they tampered with on-site camera equipment to make a computer-generated mushroom cloud appear in a panorama shot during a weather forecast.

As technology improves, more and more broadcasts will be automated. It will be a ripe environment for future pirates.