What Is A Sleeper Cell? And Should Americans Be Worried?

Growing tensions in Iran have recently brought more attention to the term “sleeper cells.” While it may sound like something from an action movie, it’s a real concept often discussed in intelligence and national security circles.

Federal officials have received intercepted communications from Iran believed to be “an operational trigger” for sleeper cells.

The topic has come up more frequently after continued strikes across the region following the death of Iran’s Supreme Leader, Ayatollah Ali Khamenei, who was killed in a joint U.S.–Israeli attack on Feb. 28. According to a federal alert obtained by ABC News on March 9, U.S. officials intercepted encrypted communications believed to have come from Iran. Authorities say the message could potentially act as what officials described as “an operational trigger” for sleeper agents located outside the country.

Investigators say the message was sent shortly after Khamenei’s death and was relayed across several countries. The communication was reportedly encoded and meant for “clandestine recipients” who would have the key needed to decode it. Messages like this are designed to send instructions to covert operatives or sleeper agents without using the internet or cell phone networks, which makes them harder to trace.

Officials say the message could “be intended to activate or provide instructions to prepositioned sleeper cell agents “operating outside the originating country.” At the same time, authorities stressed that there is currently no specific threat tied to any location. Law enforcement agencies were simply advised to keep a closer watch on unusual radio-frequency activity. 

What is a sleeper cell?

In simple terms, a sleeper cell is a group of secret agents who live in another country and appear to live normal lives. They may work regular jobs, have families, and blend into everyday society. However, they remain inactive for long periods of time until they receive instructions to carry out a mission. Those missions could include things like spying, sabotage, or terrorist attacks. Because sleeper cells are designed to blend in with the public, they can be very difficult for intelligence agencies to detect.

Notably, in 2025, FBI Director Kash Patel increased efforts to monitor potential domestic sleeper cells linked to Hezbollah, a U.S.-designated foreign terrorist organization backed by Iran. According to CBS News, the heightened monitoring began after Israel launched its Operation Rising Lion offensive, prompting U.S. officials to intensify surveillance of possible threats.

Should we be worried? Here’s what former FBI Agent Stuart Kaplan had to say.

WPBF 25 News spoke with Stuart Kaplan, an attorney and former FBI agent, on March 2 about what sleeper cells are and why they can be dangerous. Kaplan explained that these groups typically enter the U.S. with the support of people here on home soil or abroad to carry out  “some sort of act of violence or destruction that would interrupt our daily lives.”

Typically, the FBI is able to work swiftly to “identify and dismantle” their nefarious plans. The expert said that the efforts to identify sleeper cells happen quietly behind the scenes. While people may hear about threats in the news, much of the work to prevent them happens without public attention.

“We may never hear about them because they are encompassed in our national security efforts, and those individuals who may be identified may be apprehended and may be dealt with in a manner that is not known to the public,” he continued. “So, look, at the end of the day, the FBI is tasked with counterintelligence and national security here in the United States, and they are working around the clock to identify and neutralize those potential sleeper cells.”

Kaplan also said that if a sleeper cell attack were to happen on U.S. soil, it may not necessarily come directly from Iran. Instead, other countries that have tense relationships with the United States could potentially be involved.

“I think what the FBI is more concerned about is that there are other state-sponsored actors that could potentially be funded through the Chinese or through Russia that may have little to no identifiable aspects to Iran,” he added. “Because the Chinese or the Russians are interested in disrupting our democracy and our everyday way of life, those are the potential issues that the FBI is dealing with right now. While we’re focused on Iran, we know that the Chinese and the Russians would love to disrupt our democracy, and so there are many different faces, moving parts that the FBI has to be focused on. We can’t just have tunnel vision, a one-dimensional look at this. There’s a multi-dimensional look at who potentially can come at us and hopefully be able to identify and neutralize those threats before they carry out anything here on our home soil.”

For now, officials continue to say there is no confirmed threat connected to the intercepted communication, but security agencies remain alert as tensions around the world continue to evolve.

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