You already know that laptops, desktop computers, tablets and mobile phones are all at risk of being hacked. But did you know that intruders might use the built-in camera to take surreptitious pictures and videos of you and your surroundings or hijack your microphone to eavesdrop on conversations?

The latest story from the Edward Snowden leaks yesterday drives home that the NSA and its spy partners possess specialized tools for doing exactly that. According to The Intercept, the NSA uses a plug-in called GUMFISH to take over cameras on infected machines and snap photos.

Another NSA plug-in called CAPTIVATEDAUDIENCE hijacks the microphone on targeted computers to record conversations.

Intelligence agencies have been turning computers into listening devices for at least a decade, as evidenced by the Flame spy tool uncovered by Kaspersky Lab in 2012, which had the ability to surreptitiously turn on webcams and microphones and perform a host of other espionage operations. Researchers believe Flame has been around since 2007.

But it's not just the NSA who can hijack your webcam and mic. Cybercriminals, sextortionists, law enforcement, and even school districts have all been doing this kind of spying for a number of years.

Spy tools, whether designed by intelligence agencies, cyber crooks or internet creeps, can turn your camera on without illuminating the indicator light. Naturally, there are even online tutorials available to instruct neophyte hackers on how to hijack your webcam.

Fortunately, WIRED is here with a solution: Cover your camera lens with a sticker.

It's low-tech, to be sure. But it works.

A sticker is better than a Post-It, which can lose its adhesion and fall off. Gaffer tape works nicely, too, but can leave a residue.

The Electronic Frontier Foundation has created webcam stickers that you can order for justfive bucks. The black vinyl emblems are designed with a special adhesive that won't leave a residue on the camera lens when you remove it. With EFF's logo on them, they also make a civil liberties statement.

If you want to make a more stylish statement, however, Etsy offers several options, including a Hello Kitty web cam cover, emoticon stickers, and a pink skull-and-crossbones for laptop cams, and a crocheted ghost cozy for external web cams.

If you use your laptop camera often for Skyping and video conferencing, you might prefer the C-slide, which uses a sliding door to cover and uncover your camera's eye.

Sadly, covering your camera still won't prevent spies, intruders and even web sites and phone apps from surreptitiously turning on the internal microphone on your computer or mobile phone, computer, or VoIP phone and listening in on conversations.

Muting the mic won't work, since it's possible for an intruder to unmute it. Your best defense is probably to insert a dummy plug into the microphone jack to prevent sound from being picked up by the internal mic. You can create a dummy plug by simply cutting off the unneeded portion of an old microphone plug. This won't prevent someone from listening to your conversations when you need the mic, such as when using Skype, but it will at least thwart them from using the microphone on their own without you knowing.