Explained: What are Iranian sleeper cells—and why is the FBI on high alert?

The United States, as per reports, has stepped up surveillance of Iranian sleeper cells. As things heat up in the Middle East with the US joining Israel's war against Iran and its nuclear programme, America has reportedly stepped up surveillance of Iran-backed operatives in the country. FBI Director Kash Patel has asked his team to step up efforts to monitor possible sleeper cells linked to Hezbollah, a designated foreign terrorist organisation.

Why is the US worried?

As per a CBS News report citing anonymous sources, the increased surveillance comes after Israel's Operation Rising Lion offensive began earlier this month.

For years, America has been worried about sleeper cells and Tehran's ability to direct or inspire attacks. However, the threat of Iranian operatives has become a major cause of worry for United States administrations, both current and previous, since Iranian General Qasem Soleimani's assassination during Donald Trump's first term in January 2020.

As the US officially enters the Israel-Iran conflict, Tehran or its proxies, including Hezbollah, could activate dormant networks on US soil, which is why the FBI is sounding alarms—and why surveillance is ramping up—now, before any activation occurs. But what exactly are sleeper cells? Here's all you need to know.

What are sleeper cells?

Sleeper cells are the term used to refer to covert operatives that are embedded in a target country with no immediate mission until activated or called to action by their operatives.

These operatives often live quiet, unassuming lives, fully assimilated—working regular jobs, holding down routine roles—until they suddenly "wake up" to execute a mission. Sleeper cells are arguably the most insidious and unpredictable threat, because these operatives hide in plain sight, often invisible until it's too late.

The US Department of Homeland Security has once again sounded the alarm on Iran's global threat posture, warning that the Islamic Republic is expected to continue sponsoring terrorism and plotting attacks against individuals, including current and former American officials. The latest assessment echoes a similar report issued by DHS under the Biden administration in 2024.

Mike Nelson, a retired Special Forces lieutenant colonel with CENTCOM experience, told News Nation that Hezbollah has had sleeper cells in the western hemisphere for some time, including coming through Venezuela. He said that Iranians and Hezbollah have used these cells in the past, including during the Jewish Community Centre bombing in Buenos Aires in 1994.

"It seems likely (Hezbollah and Iran) would try to activate sleeper cells in the United States as retaliation if the U.S. joins in the strikes, so it would be prudent for the FBI to be monitoring," said Nelson.

According to Nelson, Iran’s regime views its survival as the endgame. "The Iranian regime wants this to end with them in power, and their primary concern is survival," he said.