You do realize that the director essentially mirrored what Obama says when ISIS is loosing ground? As they loose ground they will increase attacks on soft targets...
"The resources needed for terrorism are very modest, and the group would have to suffer even heavier losses of territory, manpower and money for its terrorist capacity to decline significantly," Brennan added. "In fact, as the pressure mounts on ISIL, we judge that it will intensify its global terror campaign to maintain its dominance of the global terrorism agenda."... The CIA director noted that ISIS has lost "large stretches" of territory in Iraq and Syria, has experienced a reduction of finances, and has struggled to replenish its ranks as fewer foreign fighters have been traveling to those countries."
And more from his testimony:
"On the battlefields of Syria and Iraq, the U.S-led coalition has made important progress against ISIL. The group appears to be a long way from realizing the vision that Abu Bakr al-Baghdadi laid out when he declared the “caliphate” two years ago in Mosul.... Several notable indicators are trending in the right direction. ISIL has lost large stretches of territory in both Syria and Iraq. Its finance and media operations have been squeezed. And it has struggled to replenish its ranks of fighters, in part because fewer foreign fighters are traveling to Syria. Moreover, some reports suggest that a growing number of ISIL members are becoming disillusioned with the group and are eager to follow in the footsteps of members who have already defected... In sum, ISIL remains a formidable adversary, but the United States and our global partners have succeeded in putting the group on the defensive, forcing it to devote more time and energy to try to hold territory and to protect its vital infrastructure."
https://www.cia.gov/news-informatio...nan-as-prepared-for-delivery-before-ssci.html
In summary... ISIS is loosing on the battlefield. They are on the defensive and loosing more and more land, more and more fighters, and more and more resources. However as he essentially said committing terrorist attacks on soft targets takes little resources and unfortunately are pretty hard to prevent.