Add Yahoo as a preferred source to see more of our stories on Google. ABC News contributors Robert Boyce and Javed Ali break down how intelligence agencies work to stop sleeper cell threats.

The death of Iran’s Supreme Leader Ali Khamenei on February 28 has reportedly triggered a series of covert communications that have raised concerns among intelligence agencies across the world.

Iran's sleeper cell threat in the U.S. after military base attack: Did Trump act on G7 intel? The story around Iran’s sleeper cell threat in the U.S. has turned urgent after Iran launched a missile ...

Concerns about potential Iran-linked sleeper cells are rising as the Department of Homeland Security remains unfunded and Tehran and its proxies threaten retaliation over U.S.-Israeli strikes that ...