WASHINGTON—A group of five U.S. senators urged the Federal Communications Commission (FCC) on Wednesday to address surveillance threats posed by foreign firms providing services to U.S. telecommunications providers. The previously unreported letter, led by Sen. Ron Wyden (D-Ore.) and also signed by Sens. Dick Durbin (D-Ill.), Richard Blumenthal (D-Conn.), Chris Van Hollen (D-Md.), and Ed Markey (D-Mass.) said it is widespread among small rural carriers “to outsource the installation and ongoing administration of networking technology to managed service providers, some of which are based in foreign countries.” The FCC has taken action in recent years to address concerns raised by U.S. telecommunications firms using hardware made by companies like China’s Huawei and ZTE Corp. The Democratic lawmakers said the FCC should work with U.S. intelligence agencies “to identify high-risk foreign managed service providers that pose a threat to Americans’ privacy and U.S. national security and prohibit U.S. wireless carriers from …