"Historically, we know quite a bit about these networks," CBS News Senior National Security Analyst Juan Zarate said. In fact, he pointed out, the leader of ISIS, Abu Bakr al-Baghdadi, was once in U.S. custody.
What is not known, he said, is whether ISIS "is really a group just devoted to the regional goals of establishing an Islamic caliphate, or if at the same time they are developing global -- not just ambitions but capabilities -- to attack the West."
There's no doubt that the extremist group, borne out of al Qaeda in Iraq, has been able to build momentum and succeed where Osama bin Laden couldn't -- in establishing an Islamic state in the Middle East.
"I think U.S. officials have discounted too much the symbolic importance of what they've done to establish the Islamic state," Zarate said. "You can argue about whether or not it's going to outlive the environment, but the reality is they've done it."
That's creating enthusiasm, he said, that is enabling the group to recruit globally in addition to "piggy-backing off the groups al Qaeda has already built."
ISIS is, in fact, a rival to the current iteration of al Qaeda. ISIS was spun off from its network in February because it disobeyed orders from al Qaeda leader Ayman al-Zawahri. However, ISIS has its origins in al Qaeda in Iraq and once called itself the Islamic State of Iraq.
The group gained momentum in the security vacuum in Syria, where it gained resources, territory and fighters, Zarate said.
The group has built an "extensive network," said Brian Katulis, a senior fellow at the left-leaning Center for American Progress, by crafting "tactical alliances of convenience" with groups like the ex-Baathists in Iraq and tribal elements.
"What they've done that's unique is they've tapped into the dissent in the society, both in Iraq and Syria," Katulis said.
While ISIS is brutally and aggressively using force to expand its power, it is "also going to the commanding heights of these economies," Katulis said, "going to dams, going to control the electricity and other basic aspects of life... What they're doing is tapping into the sense of grievance that many Iraqis and Syrians have about their governance."
As dysfunctional as the political governance in Iraq is, there's still movement, Katulis noted, leaving hope for improvements that could blunt the momentum ISIS has built.
Prime Minister Nouri al-Maliki has refused to step down from his post. However, Iraq's new president Fuad Masum on Monday nominated the deputy parliament speaker, Haider al-Ibadi, to form a new government within 30 days.
On the other hand, the support ISIS is receiving isn't coming solely from Iraq and Syria.
"There's also this other dimension, sectarianism that's going on in the region," Katulis said. "There's clear evidence there are some backers from Gulf states that are oil rich that have supported some elements of this this group.
"If we want to squeeze this group, we need to deal with all of their sources of support," he said.