Amman, Jordan — Hacker-activists across the world have launched an online war against the so-called Islamic State, targeting the web-savvy jihadists’ vast Internet network of supporters and suspected sleeper cells. But bureaucracy at a wary FBI and stringent US laws against hacking are slowing these efforts to take down the IS web forums and social media accounts, experts and analysts say. As a result, they say, the jihadists are opting to base their web operations on US-hosted sites in order to take advantage of US legal protections. Various groups of anonymous citizen hackers are taking on the jihadists, including Ghost...