US officials warn of encrypted communications by extremists

The growing use of encrypted communications and private messaging by supporters of the Islamic State group is complicating efforts to monitor terror suspects and extremists, U.S. law enforcement officials said Wednesday.

Appearing before the House Homeland Security Committee, the officials said that even as thousands of Islamic State group followers around the world share public communications on Twitter, some are exploiting social media platforms that allow them to shield their messages from law enforcement.

"There are 200-plus social media companies. Some of these companies build their business model around end-to-end encryption," said Michael Steinbach, head of the FBI's counterterrorism division. "There is no ability currently for us to see that" communication, he said.

Asked later in the hearing if he thought the technology companies were being unhelpful, Steinbach replied, "The companies have built a product that doesn't allow them to help."

He said he was concerned that evolving technologies were outpacing laws that allow law enforcement to intercept communications by suspects.

"We are striving to ensure appropriate, lawful collection remains available," Steinbach said in his prepared remarks.

John Mulligan, the deputy director of the National Counterterrorism Center, testified that one of the two men involved last month in an attempted terror attack in Garland, Texas, asked fellow Islamic State supporters before the shooting to move their communications to private Twitter messages. Those men, Elton Simpson and Nadir Soofi, were fatally shot by police after opening fire outside a provocative Prophet Mohammed cartoon contest. No one else was killed.

The hearing also took place one day after police in Boston shot a man under 24-hour surveillance by terrorism investigators when he lunged with a large knife at officers outside a CVS pharmacy. The FBI said Wednesday that the man, Usaama Rahim, plotted for at least a week to attack police and was confronted because he had purchased knives and talked of an imminent attack on "boys in blue."

"These cases are a reminder of the dangers posed by individuals radicalized through social media," said Rep. Michael McCaul, a Texas Republican and chairman of the committee.

FBI Director James Comey has expressed repeated concern about the ease with which the Islamic State group is able to spread its propaganda to supporters online and to people determined to reach Syria to join the conflict there.

More than 180 U.S. residents and about 4,000 Westerners in all have traveled or attempted to travel to Syria, officials said Wednesday.