Virtual Jihad -- The Internet as the ideal terrorism recruiting tool / Scientific American, 26 Dec 2005

http://www.freerepublic.com/focus/f-news/1550505/posts
Luis Miguel Ariza,
"According to Gabriel Weimann, a professor of communications at the University of Haifa in Israel, the number of all terrorist Web sites--those advocating or inciting terrorism or political violence--has grown from a dozen in 1997 to almost 4,700 today, a nearly 400-fold increase. (By comparison, the total number of Web sites has risen about 50- to 100-fold.) The enumeration includes various Marxist, Nazi and racist groups, but by far the dominant type, according to Weimann, is the Islamist-jihadist variety, which accounts for about 70 percent. "