FBI Director James Comey admitted to lawmakers that ISIS and other terrorist groups are using encryption methods as a way to avoid federal investigators.

“This is not your grandfather’s al Qaeda,” he told a Senate panel.

Comey said that ISIS has been effective in using social media outlets like Twitter where they have over 22,000 English-language followers.

“[It’s like a] devil in their pocket all day long that says ‘Kill, kill, kill,” Comey said.  “There is simply no doubt that bad people can communicate with impunity in a world of universal strong encryption.”

“We cannot break strong encryption,” Comey told lawmakers on the Senate Intelligence Committee. “I think people watch TV and think the bureau can do lots of things. We cannot break strong encryption.”

Comey cited as an example the case of Usaamah Rahim, the Boston man killed when he attacked FBI and Boston Police as they tried to question him.  The agents tracking him couldn’t see his exact plans because they went into an encrypted site.

The FBI calls that “going dark.”

“ISIL does something al-Qaida would never imagine: they test people by tasking them,” Comey told the senators. “Kill somebody and we’ll see if you are really a believer. And these people react in a way that is very difficult to predict. What you saw in Boston is what the experts say is flash-to-bang being very close. You had a guy who was in touch in an encrypted way with these ISIL recruiters and we believe was bent on doing something on July 4th. He woke up one morning, June 2nd, and decided he was going to go kill somebody.”