News of the terrorist attack in Tel Aviv’s Sarona Market had barely broken Wednesday night when Hamas leader Ismail Haniyeh took to Twitter to praise the slaughter.“One of the #TelAviv bomber heroes. Mercy and light on the kindness of your soul,” the former Hamas prime minister tweeted in Arabic at 10:45 p.m., alongside a picture of one of the attackers, shot in the street.Haniyeh’s Twitter account has been active since March 2012, and has 314,000 followers.Khaled Mashaal, the group’s leader, has had an account active since last May, now with 45,800 followers. The main Hamas Twitter page, active since October 2010, has 239,000 followers. It even has an English-language account to helpfully convey the organization’s support of shooting innocents at a shopping center, dubbing it “a natural response to Israeli crimes.”What some Israeli counter-terrorism experts want to know is why Twitter, a US-based company, is not shutting down accounts belonging to organizations that the United States designates as terrorist groups.“Essentially, the war against radical Islamic terror is occurring over social media,” said Uzi Shaya, a former senior intelligence official. “So Twitter is facilitating terror, with full knowledge,” he added.Shaya admitted that the US government may lack legal support for shutting down social media pages for groups designated as terrorists, and says that legislation should be taken up to further the cause.But Twitter, he noted, can act on its own.“Twitter is protected by a law of freedom of expression in the United States, but this is an absurd argument,” he said.Entities that are barred from opening a US bank account, he argues, should not be given a platform to spread their ideas through American companies.Beyond legal action, Twitter’s own terms of service explicitly ban support for terrorism.Accounts that “make threats of violence or promote violence, including threatening or promoting terrorism,” may be suspended temporarily or permanently, the terms say. Further, they ban “hateful conduct,” which includes promoting violence, attacking or threatening others on the basis of, among other thing, national origin or religious affiliation.Twitter has acted on these problems in the past.In February, the company said that it had suspended 125,000 ISIS-linked accounts over the course of six months, that it was “horrified by the atrocities perpetrated by extremist groups,” and that it condemned such behavior.Indeed, it has also taken action against Hamas in the past, but unevenly.“There is not always a rhyme or reason,” said Steve Stalinsky, the executive director of MEMRI, a group that monitors and translates extremist content from the Middle East with the aim of influencing US policy.MEMRI, he said, has been monitoring jihadist and terrorist groups on Twitter for about 5 years, “and there’s always been ebbs and flows on removing content.“When we issued a report on the Kassam Brigades [the armed wing of Hamas], it was taken down right away. But then it came back,” he said.Twitter, which did not return requests for comment, said in its February blog post that it is working hard to identify and remove terrorist accounts, working with law enforcement, international bodies, foreign governments and NGOs to remove such pages.“As many experts and other companies have noted, there is no ‘magic algorithm’ for identifying terrorist content on the Internet, so global online platforms are forced to make challenging judgment calls based on very limited information and guidance,” the post said, alongside a vow to “aggressively enforce” the rules in the area.But with the exception of the Izzadin Kassam Brigades, whose current account dates back 13 months, many of the current official Hamas pages have been around for years without interruption.Shaya believes the company is still holding back on acting against Hamas pages.“It’s not that they’re hiding their identity. They’re not. Terrorist organizations that are defined as terrorist organizations all over the world have pages on Twitter,” he said.When lawsuits linking terrorist social media accounts to specific attacks start rolling in, he suggested, the behavior might change, though legal experts believe such suits would face difficulties.Still, Twitter’s announcement on the ISIS account purge came just a month after Tamara Fields, an American woman who lost her husband to an ISIS attack, filed a lawsuit against the social media company.