US intelligence agencies have issued a security alert after intercepting an encrypted transmission that may signal the activation of Iranian “sleeper assets” operating overseas. The warning comes as the conflict involving the United States, Israel and Iran continues to intensify across the Middle East.
According to intelligence officials, the coded message appeared shortly after the death of Iran’s Supreme Leader Ali Khamenei on February 28. Investigators believe the signal may contain instructions for covert operatives positioned outside Iran.
Authorities say the message was transmitted through a broadcast system designed to deliver instructions secretly to agents who possess the required encryption keys.
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US agencies believe the message could serve as an “operational trigger” intended for hidden operatives stationed in different countries. These agents, often called sleeper assets, typically live quietly until they receive instructions to act.
A federal alert circulated among law enforcement agencies described the possible purpose of the broadcast.
“The alert warned that the message could “be intended to activate or provide instructions to prepositioned sleeper assets operating outside the originating country.”
Officials explained that the encrypted transmission appeared to target specific recipients rather than the public. Because of the strong encryption used, analysts have not yet been able to decode the exact instructions contained in the message.
The memo also said intelligence teams detected a radio station repeatedly broadcasting the signal internationally.
“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.”
Authorities said the alert does not point to any confirmed attack plan but advised agencies to monitor suspicious radio signals and communications.
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The warning has prompted heightened vigilance across US intelligence and law enforcement agencies. Security officials say they are closely watching any unusual activity that could signal a potential threat.
Counterterrorism teams have also intensified surveillance of extremist networks that might respond to the ongoing war.
“If ever there’s going to be a Hezbollah cell or a Hamas cell act in the United States in a violent way, it’s now,” Chris Swecker, a former assistant FBI director, told Fox News soon after the conflict broke out.
Following US airstrikes on Iran earlier in the conflict, FBI Director Kash Patel confirmed that authorities had increased security preparations nationwide.
He wrote on X that he had ordered “counterterrorism and intelligence teams to be on high alert and mobilise all assisting security assets needed”.
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US President Donald Trump also addressed the possibility that Iran or its allies could attempt retaliation on American soil.
“I guess … We think about it all the time. We plan for it. But yeah, you know, we expect some things. As I said, some people will die. When you go to war, some people will die.”
Security officials say they are preparing for multiple scenarios, including cyber threats, covert operations or attacks carried out by militant groups linked to Iran.
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Local governments in several major American cities have already increased security patrols as a precaution. Authorities in cities including Los Angeles, Miami and New York have deployed additional police around locations considered sensitive targets.
Officials are focusing on places such as religious institutions, cultural centres, and schools, where large numbers of people gather.
The security alert comes as the broader Middle East conflict continues to expand. Israel has carried out strikes on Iranian targets and Iran-backed Hezbollah positions in Lebanon, while militant groups have continued launching rockets into Israeli territory.
Intelligence experts warn that as the conflict intensifies, the risk of indirect attacks or covert operations in other parts of the world could increase. For now, US authorities say they remain on high alert while monitoring the encrypted transmissions and potential threats linked to them.
