Ever since terrorists started using the internet, amateur crusaders, lawmakers and others have tried to fight back, pressuring technology companies to shut out the militants. So it was only a matter of time before the war on terrorist media went social.

On Thursday, an Israeli legal advocacy group Shurat HaDin threatened Twitter with a lawsuit if it didn’t remove the accounts of U.S.-designated Foreign Terrorist Organizations such as the Lebanon-based Hezbollah and Somalia’s al-Qaida-linked al-Shabaab. Though a legal tussle may give the folks at Twitter a headache, the terrorists behind the...

Not many people think of shantytowns, illegal street vendors, and unlicensed roadside hawkers as major economic players. But according to journalist Robert Neuwirth, that’s exactly what they’ve become. In his new book, Stealth of Nations: The Global Rise of the Informal Economy, Neuwirth points out that small, illegal, off-the-books businesses collectively account for trillions of dollars in commerce and employ fully half the world’s workers. Further, he says, these enterprises are c...