Social media and other technology are making it increasingly difficult to combat militants who are using such modern resources to share information and conduct operations, the head of the U.S. Central Intelligence Agency said on Friday.

CIA Director John Brennan, in a speech in New York, said such communications heighten the challenge of dealing with diffuse threats and attacks across the world from groups like Islamic State or known as the self-proclaimed Islamic State in Iraq and al-Sham, ISIS.

"New technologies can help groups like ISIL coordinate operations, attract new recruits, disseminate propaganda, and inspire sympathizers across the globe to act in their name," Brennan said, using an acronym for the militant group that has taken hold in Syria and Iraq.

"The overall threat of terrorism is greatly amplified by today's interconnected world, where an incident in one corner of the globe can instantly spark a reaction thousands of miles away; and where a lone extremist can go online and learn how to carry out an attack without ever leaving home," Brennan said.

Speaking at the Council on Foreign Relations, Brennan cited a recent spate of attacks, including shootings at the French satirical newspaper Charlie Hebdo, at a Pakistani school, and at a cafe in Copenhagen, Denmark.

"These attacks underscore a disturbing trend that we have been monitoring for some time: The emergence of a terrorist threat that is increasingly decentralized, difficult to track, and difficult to thwart," he said.

While U.S. agencies have boosted efforts against cyber-based threats, those bent on committing acts of terrorism have also improved their use of technologies, Brennan said.

The Islamic State militants have used social media and other technology to grow into a global movement that attracts recruits by romanticizing its narrative in places like Syria and Iraq, he said.

"This phenomenon now has generated a lot of appeal" Brennan said. "We see these different franchises ... that are trying to get on the bandwagon of this phenomenon and so this is a worrisome sort of global movement" requiring a broad response.

Brennan said a variety of strategies, including monitoring social media, were needed to help identify threats.

"We need to have a better sense of what's happening in the streets. And that's why looking at social media and other things you can maybe have a better sense of the barometric conditions in a country that are going to be more conducive to the forming of a storm."