A former U.S. intelligence director is warning U.S. intelligence agencies that they are underestimating the intentions and capabilities of Islamic State, a mistake that could potentially leave the country vulnerable to attacks from the extremist organization.

Derek Harvey, a former DIA advisor on Iraq, and later a Pentagon advisor on Afghanistan and Pakistan, says that the conclusions being drawn by U.S. intelligence agencies, such as the CIA, are dangerously flawed. He says that attacks in western countries are not being perpetrated by the lone wolves that these groups are assumed to be, but are part of a larger command structure that stems from the caliphate itself.

"[CIA director] John Brennan and others continue to underestimate ISIL and not understand their intent,” Harvey says. “I don’t even know if they read Dabiq [ISIL’s propaganda magazine] or their speeches closely. Their intent is to strike with organized decentralised operations focused on the West. This isn’t just lone wolves inspired by propaganda. This is coordinated.”

Key to this misunderstanding  is that Western intelligence agencies assume that ISIL is operating with behaviors similar to those of Al-Qaeda. Instead of focusing on large-scale attacks as Al-Qaeda does, ISIL prefers to perpetrate numerous small-scale attacks to induce terror. Their plans therefore can be less complicated than Al-Qaeda’s, quicker to implement, and thus can be harder for counter-intelligence groups to anticipate.

“ISIL understands that it doesn’t have to be a complicated and or complex operation like 9/11,” Harvey explains. “ISIL will put a bomb in a taxi and then send the taxi someplace, and driver won’t know he is carrying the explosive.”