The "The Onion Router," also known as Tor, is a network of servers originally developed by the U.S. government that allows users to browse the Web anonymously by sending traffic through multiple routers. It's part of the so-called Dark Web that's not indexed by search engines, and it's hard for investigators to penetrate.
What Is The Deep Web?
The groups communicate with followers through their online magazines. For years, al-Qaeda published "Inspire," which listed social media addresses where they could be reached. The ISIS version is called "The Beak," according to Stalinsky.
Extremist groups are even using messaging services found on Play Station 4 gaming consoles, a favorite of young male jihadis who particularly like "Call of Duty," according to Steven Stalinsky, executive director of the Middle Eastern Media Research Institute, a group that monitors social media by extremist groups.
"We know that foreign fighters and jihadis like to play video games," Stalinsky said. "They tweet pictures of themselves playing games, especially 'Call of Duty.' Wherever they find way to communicate, they will take advantage of it."