US intercepts Iranian signal that may activate sleeper cells abroad: Report

A man holds a picture of Iran's new Supreme Leader Ayatollah Mojtaba Khamenei (R) being handed over a folded Iranian flag by his late father Ali Khamenei (L), during a rally in support of him at Enghelab Square in central Tehran on March 9, 2026. (Photo by ATTA KENARE / AFP)

US intelligence intercepted encrypted signals likely from Iran, possibly meant to activate sleeper operatives abroad after the killing of Iran’s Supreme Leader. Authorities urge increased monitoring but say no specific operational threat has been identified.

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US intelligence agencies have intercepted encrypted communications believed to have originated in Iran that may serve as a potential trigger for sleeper operatives abroad, according to a federal alert circulated among law enforcement agencies.

The alert, reviewed by ABC News, refers to “preliminary signals analysis” of a transmission that is “likely of Iranian origin”. The communication was reportedly relayed across several countries shortly after the killing of Iran’s Supreme Leader Ayatollah Ali Khamenei in a US and Israeli strike on February 28.

Officials say the intercepted signal was encoded and appeared to be directed at “clandestine recipients” who possess the necessary encryption key. Such transmissions are typically designed to deliver instructions to “covert operatives or sleeper assets” without relying on conventional communication systems such as the internet or cellular networks.

According to the alert, it is possible that the signals could “be intended to activate or provide instructions to prepositioned sleeper assets operating outside the originating country”.

Authorities have not yet been able to determine the exact content of the communication.

“While the exact contents of these transmissions cannot currently be determined, the sudden appearance of a new station with international rebroadcast characteristics warrants heightened situational awareness,” the alert said.

Despite the concerns raised by the intercepted signal, the notice emphasises that there is currently “no operational threat tied to a specific location”.

However, the advisory instructs law enforcement agencies to increase monitoring of suspicious radio frequency activity in order to detect any potential follow up communications.

The development comes amid heightened security concerns following the strike that killed Khamenei. Law enforcement officials have warned that Iran could attempt to retaliate through covert networks or sleeper cells operating in Western countries.

If confirmed, the intercepted transmissions could indicate that Iran is attempting to communicate with operatives positioned outside its borders without relying on digital communication channels that are easier for intelligence agencies to monitor.