CIA Director John O. Brennan said Monday the Islamic State has developed an “external operations agenda” to conduct deadly attacks beyond its self-declared caliphate in Syria and Iraq, and he warned that the extremist group likely has operations similar to last week’s bloody rampage in Paris “in the pipeline.”

The remarks were Brennan’s first public comments since assailants carried out a coordinated series of shootings and suicide bombings across the French capital on Friday that left at least 129 people dead. The Islamic State has claimed responsibility for the attacks, and France has blamed the extremist group for the violence.

“I certainly would not consider it 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,” Brennan said at a Washington think tank. “This is not something that was done in a matter of days. This was something that was deliberately and carefully planned over the course of, I think, several months in terms of making sure that they had the operatives, the weapons, the explosives, the suicide belts.”

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On Monday, security forces in France and Belgium were carrying out a series of raids in search of people with suspected links to the attacks.

Looking ahead, Brennan expects the Islamic State to try to conduct more strikes like the ones in Paris, and that “security and intelligence services right now in Europe and other places are working furiously to see what else they can do in terms of uncovering them.”

But European countries, many of whom have seen hundreds of citizens travel to Syria and Iraq to join extremist groups like the Islamic State, face an uphill climb trying to keep tabs on everyone of potential interest.

“There is an overwhelming number now of cases that they need to pursue,” he said. “A lot of our partners right now in Europe are facing a lot of challenges in terms of the numbers of individuals who have traveled to Syria and Iraq and back again, and so their ability to monitor and surveil all these individuals is under strain.”

In many regards, the attacks in Paris were not a surprise, Brennan said. The United States and its allies had “strategic warning” and knew that “plotting by ISIL was underway, looking at Europe in particular as the venue for carrying out these attacks,” he said.

But the ability of Western intelligence agencies and their allies to penetrate Islamic State networks or snoop on the militants has grown increasingly difficult.

“There has been a significant increase in the operational security of a number of these operatives and terrorist networks as they have gone to school on what it is that they need to do to keep their activities concealed from the authorities,” Brennan said.

“There are a lot of technological capabilities that are available right now that make it exceptionally difficult, both technically as well as legally, for intelligence and security services to have the insight that they need to uncover it,” he added.

Encryption Debate

With those comments, Brennan appeared to be wading into the contentious dispute in the United States over encrypted communications. Senior American officials, including the directors of the FBI and NSA, have repeatedly argued for special access to end-to-end encrypted messaging services on such technology as mobile phones, saying it is necessary to help thwart terrorist and criminal plots.

Supporters of strong encryption, meanwhile, argue that the benefits far outweigh the potential pitfalls. They also point out that authorities have yet to provide any evidence that terrorism or criminal investigations have been thwarted by encrypted communications.

There is no public evidence, so far, that the terrorists behind the Paris attacks used encryption to conceal the operation from authorities.

Still, Brennan used the opportunity to call for a change in how the public perceives encryption.

“In the past several years because of a number of unauthorized disclosures, and a lot of hand-wringing over the government’s role in the effort to try to uncover these terrorists, there have been some policy and legal and other actions taken that make our ability, collectively, internationally, to find these terrorists much more challenging,” he said.

“I do hope that this is going to be a wakeup call, particularly in areas of Europe, where I think there has been a misrepresentation of what the intelligence and security services are doing by some quarters that are designed to undercut those capabilities.”