A large spike in suspicious activity on a major U.S. cellular carrier has raised red flags in the Department of Homeland Security and prompted concerns that cellphones in the region are being tracked. Such activity could allow pernicious actors to clone devices and other mobile equipment used by civilians and government insiders, according to information obtained by the Free Beacon...

Cell phone information gathered by the program shows major anomalies in the D.C.-area indicating that a third-party is tracking en-masse a large number of cellphones. Such a tactic could be used to clone phones, introduce malware to facilitate spying, and track government phones being used by officials in the area.

"The attack was first seen in D.C. but was later seen on other sensors across the USA," according to one source familiar with the situation. "A sensor located close to the White House and another over near the Pentagon have been part of those that have seen this tracking."

The story goes on to say the attack on the network is ongoing. The identity of the group behind the attack is unknown but the Free Beacon notes the scale of the attack could indicate a foreign nation is involved. Buzzfeed has a follow-up report identifying the network in question as T-Mobile and offering a bit more detail on the type of attack:
Posted by: Besoeker 2017-03-19