A bipartisan group of senators is pushing the Department of Homeland Security (DHS) to make public more information about the use of rogue surveillance devices colloquially known as “Stingrays.”

Homeland Security recently acknowledged the devices are being used by hostile actors in Washington, D.C.

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The use of those devices by criminals and foreign spies to eavesdrop on cellphone calls and messages in the U.S. has long been suspected, but the department's disclosure was the first official confirmation of their presence.

But it left many questions unanswered, like what kind of devices the DHS had uncovered, who might have been using them and how many it found.

Sens. Cory Gardner Cory Scott GardnerOvernight Health Care: US coronavirus deaths hit 200,000 | Ginsburg's death puts future of ObamaCare at risk | Federal panel delays vote on initial COVID-19 vaccine distribution The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-Colo.), Ron Wyden Ronald (Ron) Lee WydenGOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate GOP senator blocks Schumer resolution aimed at Biden probe as tensions run high MORE (D-Ore.), Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (R-Ky.) and Ed Markey Edward (Ed) John MarkeySchumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Democrats see fundraising spike following Ginsburg death Democratic senator calls for eliminating filibuster, expanding Supreme Court if GOP fills vacancy MORE (D-Mass.) are calling on the DHS to release an unclassified PowerPoint presentation detailing the threat.

The presentation was given by a DHS official at the Federal Mobile Technology Forum in Mclean, Va., in February, according to the four lawmakers.

They described the presentation as “detailed,” but gave no other details about what it reveals.

“The American people have a legitimate interest in understanding the extent to which U.S. telephone networks are vulnerable to surveillance and are being actively exploited by hostile actors,” they wrote in a letter to DHS official Christopher Krebs.

So-called International Mobile Subscriber Identity-catchers, or IMSI-catchers — known as Stingrays after a popular brand used by U.S. police departments — work by tricking cellphones into locking onto the device instead of a legitimate cellphone tower. Once they are deployed, they can intercept data from a target phone.

Experts say they are widely used by foreign embassies, which are on sovereign soil, and police departments have quietly used them for years to some controversy.

The D.C. Court of Appeals last year ruled that warrantless use of the devices violated the Fourth Amendment when it was used to locate a man suspected of sexual assault and robbery — the fourth such ruling by either a state appeals or federal district court.

Wyden, meanwhile, has been calling on the Federal Communications Commission to do more to hold phone companies accountable to ensure that they safeguard their networks against security threats.

Updated at 2:02 p.m.