The move was made after the terrorist group used its Twitter feed earlier this month to threaten to murder a French hostage and again last week to threaten to kill Kenyans they had kidnapped.
Twitter’s press office failed to respond to several requests for comment Monday, but al Shabab’s page has been unavailable since Friday. “The Twitter Rules” for the microblogging site read in part: “You may not publish or post direct, specific threats of violence against others.”
The move appears to mark a policy shift from Twitter, which previously has refused or ignored requests to take down feeds used by terrorist organizations. Both the Taliban and several al Qaeda affiliates have official Twitter feeds that link to their press statements and Web releases.
In the past year, extremist groups have made increasing use of Twitter and other social networking sites after many of their traditional Internet channels — password-protected private chat rooms — closed because of sudden and unexplained technical or security problems.
The Simon Wiesenthal Center — a Los Angeles-based nonprofit group that monitors use of the Internet and social networking by terrorists and hate groups — plans to put Twitter on the cover page of its annual report, to be published in March, the center’s associate dean, Rabbi Abraham Cooper, said Monday.
“And not in a good way,” he said. “If I was grading [social media sites for blocking content that promotes terrorism], Twitter would get an ‘F’.”
“I call it the Wizard-of-Oz effect,” he said. “We don’t know who’s behind the curtain.”
“The other sites, like FaceBook or Google have developed institutional ways to respond,” he added.
“They have a set of rules. They have a staff team that looks for violations. They take down thousands of pages. It gives groups like us, or any individual user, a place to go to get an answer. ‘Will you take this down?’ We might not always like the answer, but at least we get one.
“If Twitter has a policy [against feeds that promote terrorism], they keep it a secret,” he said.
J.M. Berger, a terrorism analyst, also noted that Twitter’s rules are much less restrictive than the terms of service for other social networking sites.
“The rules are really, really broad,” he said. “You can put up stuff you would never see on YouTube or FaceBook.”