DHS and FBI Issue Elevated Alert After Intercepted Encrypted Iranian Signal Raises Sleeper Cell Activation Concerns Across U.S.

Following the death of Iranian Supreme Leader Ayatollah Ali Khamenei on March 1, 2026, and the onset of sustained U.S.-Israeli airstrikes against Iran under Operation Epic Fury, the Department of Homeland Security and FBI intercepted encrypted communications assessed to have originated from Iran that intelligence analysts characterized as a potential "operational trigger" directed at pre-positioned sleeper assets outside Iranian borders. The intercept prompted law enforcement agencies nationwide to implement enhanced monitoring protocols including heightened surveillance of known or suspected Iranian-linked individuals, increased physical security postures at federal facilities and critical infrastructure sites, and expanded monitoring of suspicious radio-frequency activity.

The FBI distributed an alert to California law enforcement agencies warning of possible Iranian-directed drone strike threats targeting the West Coast. Texas Governor Greg Abbott separately warned that Iranian sleeper cells posed a credible threat to the state following a suspicious incident in Austin. In Houston — documented by the Combating Terrorism Center at West Point and the FBI as a city where a Hezbollah-linked operative had previously stockpiled more than 300 pounds of ammonium nitrate explosive precursors — law enforcement elevated security postures at critical infrastructure and public assembly locations.

According to counterterrorism analysts and a CTC West Point assessment published during the conflict period, Iran views terrorism as an instrument of foreign policy and has maintained operational networks in the United States for decades through its primary proxy Hezbollah, which historically concentrated financial and logistics cells in New York, Houston, Detroit, Los Angeles, and Boston while deliberately placing dormant operatives in lower-profile cities including Portland, Oregon and Louisville, Kentucky. Prior to the current conflict, U.S. authorities had disrupted more than a dozen and a half Iran-connected plots on American soil, including assassination attempts against former officials and surveillance of critical infrastructure landmarks.

The DHS threat posture as of early March 2026 was described by officials as elevated but without confirmation of a specific, imminent attack. The intercept remains under active investigation, and the FBI has redirected counterterrorism personnel to cover Iran-affiliated individuals in elevated-risk jurisdictions.