CIA Director John Brennan said during an interview Sunday evening that the chances of the Islamic State in Iraq and Syria (ISIS) trying to carry out attacks on the United States is "inevitable." Appearing on CBS' "60 Minutes," Brennan said, "I'm expecting them to try to put in place - the operatives, the material or whatever else that they need to do or to incite people to carry out these attacks clearly."

"So, I believe that there attempts are inevitable," he added. "I don't think their successes necessarily are."

As the interview progressed, Brennan noted that U.S. intelligence has been successful in preventing "numerous" ISIS attacks from occurring so far, according to Newsmax"Believe me, intelligence security services have stopped numerous attacks - operatives that have been moved from maybe the Iraq to Syria theater into Europe," he said.

"They have been stopped and interdicted and arrested and detained and debriefed because of very, very good intelligence," he added.

Despite these successes however, there have been times when CIA intelligence was unable to prevent an attack. One such case was the Paris terrorist attacks on Nov. 13, 2015, that left 130 dead. Brennan said that despite having knowledge that ISIS was planning an attack "somewhere" just days before the incident, ISIS' access to encryption technology ultimately rendered the CIA's attempt to block the attack inert, according to The Hill.

"We knew just in the days before that ISIL was trying to carry out something," he said, using an alternate acronym for the group. "But the individuals involved have been able to take advantage of the newly available means of communication that are - that are walled off from law enforcement officials."

This isn't the first time Brennan has warned of imminent attacks from ISIS. Speaking at a global security forum hosted by the Center for Strategic and International Studies on the Monday after the Paris attacks, he warned that ISIS definitely has other attacks "in the pipeline."

"I certainly would not consider [Paris] a one-off event. It is clear to me that ISIL has an external agenda that they are determined to carry out these types of attacks," he said at the time.