The Department of Homeland Security has publicly stated it discovered electronic surveillance devices in Washington, DC, making it the first federal agency to do so.
These devices, known as International Mobile Subscriber Identity (IMSI) catchers, pretend to be cell towers, and intercept signals on phones to spy on calls and messages. The FBI uses similar surveillance technology through its "Stingray" program, which police officers also use.
But the US government had never spoken about foreign agents using the same technology, until DHS sent a letter March 26 to Sen. Ron Wyden, a Democrat from Oregon. The letter was first reported Tuesday by the Associated Press and obtained by CNET.
In the letter, senior DHS official Christopher Krebs said the agency had "observed anomalous activity" that was "consistent" with IMSI catchers in the US capital. The DHS said it was unclear who was behind the spying, and noted it needed more funding to better detect these devices.
Krebs, the head of the National Protection and Programs Directorate, also noted that the same "anomalous activity" had been detected outside of the nation's capital, but didn't specify where, or how many there are.
"NPPD agrees that the use of IMSI catchers by foreign governments may threaten US national and economic security," the letter noted.
Stingrays have become a controversial surveillance tool as civil liberties and privacy groups raise concerns over the suitcase-size devices that can sweep up data from entire neighborhoods. Washington is a prime target for foreign spies looking to sweep up data and information on US lawmakers, military officials and agencies.
The DHS response comes after Wyden requested answers from the agency in a letter in November asking about the presence of IMSI catchers in Washington.
Senators, including Wyden, have asked the FCC in the past to investigate Stingray technology, since the agency regulates the US airwaves. The commission formed a task force in 2014, but hasn't done much since.
"Despite repeated warnings and clear evidence that our phone networks are being exploited by foreign governments and hackers, FCC Chairman Pai has refused to hold the industry accountable and instead is prioritizing the interests of his wireless carrier friends over the security of Americans' communications," Wyden said in a statement.
The DHS didn't respond to a request for comment. In the last line of Krebs' letter to Wyden, he wrote, "overall, NPPD believes the malicious use of IMSI catchers is a real and growing risk."
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