Are all-wireless networks vulnerable to jamming?

There is much buzz about enterprise access networks going "all wireless" as the increased throughput and range of next-generation 802.11n wireless LANs become available in IEEE-standard products.

One consideration of exclusively using the unlicensed airwaves for corporate LAN access is the impact of jamming on network availability. Jamming represents a form of wireless denial-of-service attack, in that a single device transmitting at a higher power than those nearby will block connectivity to the lower-power devices. Putting all your transmission eggs in a Wi-Fi basket could mean that malicious jamming could bring your access network to its knees.

Fortunately, to date, we haven't heard much in the way of intentional, ill-intended jamming attacks on a given company or hot spot. But once enterprises go all wireless, I wonder if this will be serious security concern?

Unintentional interference is common in cell-based Wi-Fi network systems. It radiates from Bluetooth devices, microwave ovens, cordless phones, Wi-Fi access points in a neighboring office and other competitors for unlicensed spectrum. You can use spectrum analyzers, such as those offered by Cognio and its many resellers and OEMs, to detect and pinpoint such sources of interference. Then, basically, you take Ankle Express to go out and physically disable them.

But what if criminals enter the jamming game? Jamming devices exist today, primarily for legitimate testing purposes. If the jammer were within the US's FCC Part 15 regulatory power limits - 1 Watt plus 6 dBi of antenna gain, or about 4 Watts - a legitimate device could easily "out shout" most Wi-Fi devices, which typically radiate about 100 milliwatts of power, according to wireless aficionado Craig Mathias, principal at Farpoint Group.

"There are a number of jammers on the market that can completely bring 802.11 down," Mathias says. "You need some kind of radio that can localize where the source of radiation is coming from. If the jammer is illegitimate transmitting at levels above FCC limits, it could be far away and difficult to remediate."

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