On the heels of the U.S. military campaign against the Islamic State in the Middle East, a new terrorist group is emerging from the shadows according to American intelligence officials - one that may be a more sinister and direct threat to U.S. interests than ISIS.

The group, largely operating in Syria, goes by the name "Khorasan," and is a clandestine offshoot of al Qaeda.

As the New York Times reported Sunday, the group is led by senior al Qaeda operative Muhsin al-Fadhli who, according to the U.S. State Department, was "so close to Osama bin Laden that he was among a small group of people who knew about the Sept. 11, 2001, attacks before they were launched."

But the secretive group didn't come to Syria to fight amongst other "rebels" in their effort to overthrow the government of President Bashar Assad. Nor did they come to claim land or resources, as is reported of ISIS.

Rather, Khorasan members have come from Pakistan, Yemen and Afghanistan to "exploit the flood of Western jihadists" who possess valuable passports, said the Associated Press.

"They were sent by al Qaeda leader Ayman al-Zawahiri to recruit Europeans and Americans whose passports allow them to board a U.S.-bound airliner with less scrutiny from security officials," according to U.S. officials.

National intelligence director James Clapper said last week, "In terms of threat to the homeland, Khorasan may pose as much of a danger as ISIS."

Other American national security officials are now claiming - contrary to what the public may have been led to believe - that more "immediate threats [than ISIS] still come from traditional terror groups like Khorasan and the Nusra Front," reported the New York Times.

Little is actually known about Khorasan, and it's unclear how many members belong to the group, how long it has been in existence, or even what its message is.