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TI Blog - everything you need to know about Thermal Imaging

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How thermal imaging detects electronic bugs


Covert electronic surveillance – bugging – is much more common than most people think. Governments, security forces and, as we now know, the media, have been doing it for years. Even Hugh Grant’s done it successfully.

electronic bug 1It’s also an increasingly common tool for corporates, as companies spy on one another to steal intellectual property, discover competitors’ strategies and attempt to destroy rivals’ takeover plans.

But now infrared cameras are stepping in to identify bugs quickly and securely.

The scale of covert electronic surveillance

Google ‘spy shop london’ and you’ll find nearly 2.5 million results. There are around 30 dedicated spy stores doing brisk business in the UK capital alone.

Most sub-£100 bugging devices are disguised as pens, electrical plugs and even smiley face badges. They can be casually introduced into an office, left to record for a day or two, then collected. If they’re not discovered, the results can be devastating.

More sophisticated systems transmit using voice-activated GPS or LF, HF, VHF, UHF and microwave frequencies, often in very short pulses. The units, disguised as anything from laptop computers to mobile phones, ‘sleep’ until they detect a sound, so battery consumption is greatly reduced.

They can lie around for months. Even so, anything portable remains an object of interest to security officers. Plant pots, light fittings and even credit cards lying casually on a desk are inherently suspicious and are likely to be examined during any security sweep.

The hidden menace of electronic bugs

But the most dangerous electronic bugs are buried in walls and ceilings. They may have been installed many years before, when those friendly painters came in to redecorate. Lying just beneath the paint, they are impossible to see – but they listen to every word.

Electronic sweeps can identify the presence of transmitters when they are actively transmitting. However, unlike what you may see in James Bond movies, they cannot identify the precise location of a bug. Furthermore, the sweeping equipment is expensive – and bug-sweepers’ time can cost many thousands of pounds a day.

Often, the end result is a consultant telling you that there is probably a listening device somewhere in the boardroom – but you will have to destroy and rebuild that boardroom to ensure that the bug has been permanently destroyed.

Finding a reliable builder is hard enough at the best of times. Having to embark on a major rebuilding programme for an embassy or foreign business in a potentially high-risk area such as Iraq or Turkmenistan is a tall order.

Yet even the most hard-to-find bugs can now be pinpointed and disabled precisely, thanks to thermal imaging technology.

The infrared answer to electronic bugging

The principle is straightforward. When an electronic device is activated, it emits heat. By pointing an infrared camera at a blank wall, it can identify even very small changes in temperature compared with the surrounding area.

So when a few millimetres of wall heats up for just a second as the device transmits, the camera will ‘see’ and record it. A square centimetre of the structure can be investigated, and the bug found and destroyed.

Examples of where the solution has worked? Our lips are sealed. But, compared with rebuilding a boardroom, the infrared solution is elegantly simple – and another unusual use for thermal imaging technology.

[image credit:]