REUTERS/Rick Wilking
Rather than offering you cellphone service, the towers appear to be connecting to nearby phones, bypassing their encryption, and either tapping calls or reading texts.
Les Goldsmith, the CEO of ESD America, used ESD's CryptoPhone 500 to detect 17 bogus cellphone towers. ESD is a leading American defense and law enforcement technology provider based in Las Vegas.
With most phones, these fake communication towers towers are undetectable. But not for the CryptoPhone 500. It is a customized Android device that is disguised as a Samsung Galaxy S III, but has highly-advanced encryption.
Goldsmith told Popular Science: "Interceptor use in the U.S. is much higher than people had anticipated. One of our customers took a road trip from Florida to North Carolina and he found eight different interceptors on that trip. We even found one at South Point Casino in Las Vegas."
The towers were found in July, but the report implied that there may have been more out there.
Although it is unclear who owns the towers, ESD found that several of them were located near U.S. military bases.
"Whose interceptor is it? Who are they, that's listening to calls around military bases? Is it just the U.S. military, or are they foreign governments doing it? The point is: we don't really know whose they are," Goldsmith said to Popular Science.
It's probably not the NSA - that agency can tap all it wants without the need for bogus towers, VentureBeat reported:
Not the NSA, cloud security firm SilverSky CTO/SVP Andrew Jaquith told us. "The NSA doesn't need a fake tower," he said. "They can just go to the carrier" to tap your line.
ComputerWorld points out that the fake towers give themselves away by crushing down the performance of your phone from 4G to 2G while the intercept is taking place. So if you see your phone operating on a slow download signal while you're near a military base ... maybe make that call from somewhere else.
In an amazing coincidence, police departments in a handful of U.S. cities have been operating "Stingray" or "Hailstorm" towers which - you guessed it - conduct surveillance on mobile phone activity. They do that by jamming mobile phone signals, forcing phones to drop down from 4G and 3G network bands to the older, more insecure 2G band.