Fewer Americans are traveling to fight alongside the Islamic State and the power of the extremist group's brand has significantly diminished in the United States, FBI Director James Comey said Wednesday.
The FBI encountered "6, 8, 10" Americans a month in 2014 and the first half of 2015 who traveled to the Middle East or tried to go there to join the Islamic State, but that number has averaged about one a month since last summer in a sustaining downward trend, Mr. Comey said.
"There's no doubt that something has happened that is lasting, in terms of the attractiveness of the nightmare which is the Islamic State to people from the United States," he told reporters during a wide-ranging round-table discussion Wednesday.
He did not offer an explanation for the decline, though the FBI has worked aggressively in the last year to identify and intercept Americans who might be determined to reach Syria. One other possibility is that the Islamic State has encouraged more of its followers to carry out violence at home, and Comey acknowledged Wednesday that the group's ability to encourage and inspire "troubled souls" remains a persistent concern.
The FBI still has "north of 1,000" cases in which agents are trying to evaluate a subject's level of radicalization and potential for violence.
"There's still a presence online, and troubled people are still turning to this and at least being interested in it," Comey said. "But they've lost their ability to attract people to their caliphate from the United States in a material way."
After a review of the evidence, the FBI has concluded that the San Bernardino, California attack that killed 14 people in December was inspired by the Islamic State, he said.
The FBI went to court to force Apple Inc. to help it open a locked iPhone used by one of the attackers, Syed Farook, who along with his wife, Tashfeen Malik, died in a gun battle with police.
A federal magistrate granted that request in February, but the court fight ended weeks later when a still unidentified third-party came forward with a solution to access the device. Though Comey would not reveal what if any evidence was gleaned from Mr. Farook's phone, he said he was glad the FBI had gotten into the phone and that the effort was important.
The FBI last month said it did not have enough technical information about the tool that was used to get into the device to be able share the details with Apple – an assertion some outside technology specialists found curious given that Comey has hinted that the FBI paid more than $1 million for it.
But Comey said Wednesday that the FBI acquired only what was necessary to get into the one particular phone – and nothing more.
"Sometimes you can buy a tool that helps you accomplish something. Sometimes you can buy the guts of a tool, the software behind it, the code behind it – and there's a difference between those two things," he said. "The goal in San Bernardino was to investigate that case and to get into that phone, so we bought what was necessary to get into that phone – and we tried not to spend more money than we needed to spend."
He said he was not aware of another case in which the FBI had used the same workaround, but that the agency was trying to figure out a way in which it could be shared with other law enforcement agencies with valid court orders.