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Surveillance technology known as ‘Stingray’ -- used to trick phones into connecting to them by mimicking cell towers -- can block or drop phone calls and disrupt other mobile devices that use the same cell network, according to a recent court disclosure.

As RT reported last month, the American Civil Liberties Union (ACLU) recently disclosed that law enforcement officials in Florida used ‘Stingray’ surveillance to track cell phone locations on more than 1,800 occasions, all without court search warrants.

The Harris Corporation’s ‘Stingray’ is the most well known of the controversial spying technology, used by the FBI, the Secret Service, the Drug Enforcement Agency and many state and local police agencies. By impersonating cell towers, the devices force phones in the area to broadcast information that can be used to identify and locate users.

The ACLU’s recent disclosure included a court filing that uncovered the ability of 'Stingray' to negate cell phone calls by either downgrading mobile devices from 3G and 4G connectivity to 2G -- enabling them to access identification and location information -- or by the devices' "catch-and-release" operations.

“As each phone tries to connect, [the stingray device] will say, ‘I’m really busy right now so go use a different tower. So rather than catching the phone, it will release it,” Chris Soghoian, the ACLU’s chief technologist, told WIRED of the “catch-and-release” theory.

The court filing made by FBI Special Agent Michael A. Scimeca did not specify how a ‘Stingray’ would disrupt calls, only that they had the ability to do so.

“The moment it tries to connect, [the stingray] can reject every single phone” that is not the targeted phone, Soghoian added.

‘Stingray’ devices are small enough to fit in a police vehicle and can even be carried by hand. They can identify telephone numbers, unique identifying numbers, and the locations of all cell phones in range. They can also log the phone numbers called and texted by a connected phone.

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There has been much secrecy surrounding their use, as law enforcement agencies adhere to non-disclosure agreements made with the manufacturers of the devices.

“We think the fact that stingrays block or drop calls of cell phone users in the vicinity should be of concern to cell service providers, the FCC [Federal Communications Commission], and ordinary people,” Nathan Wessler, staff attorney at the ACLU Speech, Privacy & Technology Project, told WIRED.

“If an emergency or important/urgent call (to a doctor, a loved one, etc.) is blocked or dropped by this technology, that’s a serious problem.”

As WIRED noted, law enforcement have been caught using deception to justify the use of 'Stingray' devices, or they have just used the tools without a warrant. [MORE]