We know that the FBI, NSA and other agencies have the ability to scan and read our emails almost at will, but according to a report over the weekend, its surveillance capabilities extend far beyond that. In one of the creepiest revelations we’ve seen so far this year – and we’ve seen lots of creepy stuff – it’s claimed the FBI has now developed software that allows it to covertly activate web cams and spy on unsuspecting computer users.

According to the Washington Post, tech savvy spooks have developed a technique that allows them to remotely switch on web cams and transmit real-time images to investigators, without triggering that tell-tale red light which normally indicates the camera is switched on. In addition, the FBI also has the power to dig into user’s files, and download data from their machines.

The FBI’s frightening new capability was revealed following an investigation into a mysterious terror suspect named “Mo”, who threatened to plant bombs in an airport, a jail, a hotel and three college buildings unless Colorado movie-theater shooting suspect James Holmes was released from custody.

Investigators now believe the threats were a hoax, as no bombs were found at the locations he mentioned.

“Mo” is reported to made several contacts with authorities since July 2012, using either an encrypted phone or an untraceable email account. Indeed, Mo was so confident that he couldn’t be tracked, he even sent the FBI photos of himself, decked out in Iranian military fatigues.

Unable to track Mo down using conventional means, the FBI sent the suspect an email containing new software it had developed, designed to automatically install itself on his computer when he read the message. The Washington Post reports that the software was designed to help investigators track Mo’s location, but failed to work properly and so the suspect was never found.

However, a former FBI employee told the Washington Post that one of the software’s main capabilities was to give agents control over the suspect’s computer – a capability that it’s apparently had “for several years.”

It’s not clear how many times the FBI has actually tried to use the software, but the Washington Post’s source said that it only did so in the “most serious” investigations. In the case of Mo, authority to do so was granted by a Denver judge – but when agents tried to do so in another case, a Houston judge barred them from doing so, saying that the method was “extremely intrusive”.

Though few people will be surprised that the FBI possesses this kind of capability, it nevertheless remains highly controversial and has been criticized by civil rights advocates.

“We have transitioned into a world where law enforcement is hacking into people’s computers and we have never had public debate,” said Christopher Soghoian of the American Civil Liberties Union, to the paper.