US action came as Washington seeks to restore the 2015 agreement between Tehran and six major countries to freeze its nuclear program in exchange for lifting sanctions
US Justice Department officials on Tuesday announced that, with backing from a court, they purged "malicious web shells" hackers had planted in hundreds of computers running Exchange Server software.
"I was appalled that you, our country's elected leaders, were victimized right here in these very halls," Wray testified before the Senate Judiciary Committee.
"That siege was criminal behavior, pure and simple. It's behavior that we, the FBI, view as domestic terrorism."