WASHINGTON — Although al-Qaida has diminished as a working terrorist organization, it still poses a threat to the West, according to Mitchell Silber, the head of the NYPD Intelligence Division’s Analytic Unit.

On Tuesday, Silber discussed his new book, The Al-Qaeda Factor: Plots Against the West, at the New America Foundation.

Silber likened al-Qaida’s influence to a “jihadi social network” that thrives on hubs in Western cities. Through these hubs, such as mosques and Muslim student associations at universities, conspirators share ideologies that align with al-Qaida even if they are not directly affiliated with the organization, he said. Students, cab drivers, the janitor of a mosque — anyone who sympathizes with al-Qaida’s message could influence someone else to turn to militancy.

“The threat has morphed; it’s disaggregated,” he said. “But there’s still a significant threat going forward.”

Mitchell Silber discussed his book about the al-Qaida threat on Tuesday. (Rebecca Nelson/Medill)

In the 1999 plot targeting Los Angeles International Airport on the eve of the millenium, Silber said the conspirators were not affiliated with al-Qaida – but they were inspired by similar beliefs and wanted to commit violent jihad in the infamous group’s name.

Because al-Qaida’s influence extends far past the circle of active members to Western citizens, many of whom are American, Silber called this phenomenon a “bottom-up initiative.” Rather than taking orders directly from al-Qaida itself, terrorists have taken a grassroots approach to violent Jihad, rallying around al-Qaida but acting of their own volition.

This tactic is harder for intelligence analysts in the West to pinpoint, but may require the U.S. to reallocate its counterterrorism resources, Silber said.

Since 2001, the U.S. has sent troops to Afghanistan to eliminate al-Qaida forces there instead of having “more resources spent on homegrown [conspirators] to stop the supply of people who are seeking to go overseas, to disrupt them, to identify them,” he said.