As the United States on Sunday prepares to mark the 15th anniversary of the 9-11 terror attacks, Homeland Security Secretary Jeh Johnson says terror plots, unbeknownst to the public, have been disrupted “all of the time” since he started running the agency.

“We have prevented a number of actors from carrying out their intent at the very latest stages of their plotting and planning,” Johnson told Fox News on Friday.

Nearly 3,000 people were killed on Sept. 11, 2001, when al Qaeda high-jackers took down four U.S. commercial jets, including two flown into the twin World Trade Center towers.

Johnson also said the new wave of potential terror strikes is coming with little warning and in more undetectable ways.

“9-11 was the prime example of a terrorist-directed attack,” he said. “We now live with the prospect of terrorist-inspired attacks in which ISIL, al Qaeda try to literally reach into our homeland through the internet, through social media.”

Johnson made his remarks as federal employees for the first time in 15 years are working in offices at the Trade Center, rebuilt in Lower Manhattan with a memorial to the victims of the attack, which toppled the two towers.

“It goes to our resilience as Americans, as New Yorkers, as people of the free world — that we won’t let somebody else dictate what we do,” said Roger Parrino, a senior counsel for Johnson.

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