It's become standard in spy thrillers for heroes to treat their cell phones as glowing red beacons that advertise their locations. Movie-goers know that action heroes should yank the battery from their phones if they don't want to be tracked. What's less well known is that reality long ago caught up with and surpassed cinema. Using devices that essentially mimic cell phone towers, police — or anybody with one of these widgets — can get a fix on your mobile device, whether or not it's in use, and thereby on your gadget-obsessed self.

Generically salled "Stingrays," which is actually a brand name for one such International Mobile Subscriber Identity locator (you can see why "Stingray" stuck as a monicker), the Electronic Frontier Foundation says these devices work thusly:

A Stingray works by masquerading as a cell phone tower—to which your mobile phone sends signals to every 7 to 15 seconds whether you are on a call or not— and tricks your phone into connecting to it. As a result, the government can figure out who, when and to where you are calling, the precise location of every device within the range, and with some devices, even capture the content of your conversations.

Specifically, says the Wall Street Journal, "the stingray operator [can] 'ping,' or send a signal to, a phone and locate it as long as it is powered on." The Journal offers a handy visual aid to flesh out how they work:

Stingrays are in the news now because they're being used in law-enforcement cases with very sketchy legal authorization. In Maricopa County, Arizona, according to the Journal:

Sgt. Spurgin says officers often obtain court orders, but not necessarily search warrants, when using the device. To obtain a search warrant from a court, officers as a rule need to show "probable cause," which is generally defined as a reasonable belief, based on factual evidence, that a crime was committed. Lesser standards apply to other court orders.

Stopping short of full-on warrants is a matter of policy nationally, since "FBI and Department of Justice officials have also said that investigators don't need search warrants." That slippery legal authorization for tracking cell phones is at issue in United States v. Rigmaiden, in which the EFF and the ACLU have submitted an amicus brief (PDF). In that case, a court had ordered Verizon to locate the defendant, and authorities interpreted that order as authorization to use a Stingray themselves.

Complicating matters, while a Stingray is in use, it also locates every other nearby mobile device sharing that network, potentially compromising the privacy of a great many people as collateral damage.

So remember, folks. Those mobile devices we've all grown so dependent upon may be every bit as treacherous as the movies would have us believe.