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Electromagnetic sniffing is a growing security concern

While we talk a lot about the dangers of digital intrusion, some security experts and governments are becoming increasingly concerned about electromagnetic sniffing, where information is lifted as it moves through electronics by a nearby observer.

The concern is stray emissions coming from wires and circuit boards as electricity passes through them. These kind of sniffing techniques are extremely difficult to utilise, but far from impossible. At the RSA conference last year, Cryptography Research demonstrated that they could read the cryptographic key from a smartphone using only an AM radio and a few other components.

The rising concern was highlighted by Belkin's director of product management, Luis Artiz. "We know this is happening because our customers have told us that it's happening," said Artiz, referring to the commercial and government customers Belkin handles.

The targets

Artiz said that audio peripherals and KVM switches – Keyboard Video and Mouse switches, which allow users to connect those devices to multiple computers – are primary concerns in this space. He explained that this is critical for some US government clients, who can have several different classified and unclassified networks they need to use.

"These are networks in highly protected areas," he said, describing everything from foreign embassies to tents in a desert. And it's not just US agencies and companies who are worried – Artiz says he's heard the same concerns from other governments with which Belkin does business. "There are agencies who are concerned about EM sniffing," he said. "[They're] telling us that it's a major concern."

This wouldn't be the first time intelligence agencies have investigated whether electromagnetic, acoustic or other emissions could contain sensitive information. The so-called TEMPEST studies by the NSA and other groups set standards for securing electronics from emissions snooping. Other public research has looked at ways to spy on computer and television screens from a distance, like the famous Van Eck phreaking technique.

Extreme measures

Beyond EM sniffing, cross-talk between KVM channels is another major concern. Similar to the sniffing threat, crosstalk occurs when signals from one connection "leak" into another. If one of those connections is unclassified – or worse, compromised – information could be intercepted.

Artiz went on to describe some of the extreme measures he's seen people use to avoid cross-talk between channels. Some users opt for a single mouse and keyboard which they reconnect to each computer in turn, or separate keyboards and mice for each machine. Others have apparently taken to using just ports one and four of a four-port KVM switch, since these are the furthest apart.

For its part, Belkin produces National Information Assurance Partnership (NIAP) compliant KVM switches and have recently rolled out a secure audio and microphone switch, to ensure that audio information is moving to and from its intended source. The microphone products are particularly interesting since they use some decidedly low-tech countermeasures such as separate circuit boards for the mic and audio, and a manual on/off switch to prevent he microphone from being remotely activated.

Of course, the average user probably doesn't need to worry about these attacks. The techniques required to intercept and interpret information obtained via these means are neither readily accessible, nor worthwhile for most Internet ne'er-do-wells. Not as long as breaking into Twitter yields a wealth of personal information. These are the highest-end attacks, targeted at the highest level secrets, which makes the associated paranoia understandable.