U.S. officials: Encrypted apps a "blind spot" for intelligence

ISIS posts new threats online 02:05

ISIS has posted new threats online: a video purporting to be from ISIS promising an attack on Washington. But U.S. officials say there is no specific or credible threat against the United States.

On Capitol Hill, police are telling Congressional staff to "take precautions...like using the tunnels" around the capitol instead of walking above ground. In New York, a new specialized police unit is providing extra security at key locations.

SWAT teams and bomb-sniffing dogs are patrolling train stations, airports, and NFL stadiums around the country. But a response to a threat is only as good as your intelligence.

U.S. law enforcement believes one blind spot is when terrorists "go dark," hiding their online communications. Investigators say members of ISIS lure potential sympathizers to social media apps and forums where the messages self-destruct or are encrypted.

Law enforcement has been pressing the technology industry for access to that data when national security is at risk, but so far privacy concerns have won out.

"I do hope that this is going to be a wake-up call, particularly in areas of Europe where I think there has been a misrepresentation of what the intelligence security services are doing," said CIA Director John Brennan.

How could terrorists fly under the radar of s... 02:34

Brennan warns more attacks like Paris could be coming.

"I would anticipate that this is not the only operation that ISIS has in the pipeline."

The tech industry says law enforcement's calls to weaken encrypted products undermines every American's cyber security. A law enforcement source said investigators are confident the attackers were using encrypted methods of communication, but it's unclear whether investigators have the attackers cell phones and computers.