Israel reverberated with shock last week when the credit card details of 20,000 citizens were exposed on the internet, and on Monday a hacker briefly took over the website of Deputy Foreign Minister Danny Ayalon. But according to one of the country's leading web experts, these incidents are just the "tip of the iceberg" of online terrorist activity.
In a new study entitled Al Qaeda Has Sent You A Friend Request: Terrorists Using Online Social Networking, Gabriel Weimann writes that normal web users worldwide are unwittingly reading articles and watching videos posted by terrorists on a daily basis - and even accepting their "friend requests" on Facebook.
Dr Weimann, a communications professor at Haifa University, started monitoring terrorists' websites in 1998, when they numbered 12. Now he keeps tabs on 7,800. They have lively chat rooms that are "essentially online training camps". In an open forum on a Hamas website, a surfer who identified himself as Abu Jendal recently wrote "My dear brothers in Jihad. I have a kilo of acetone peroxide. I want to know how to make a bomb from it in order to blow up an army Jeep; I await your quick response." An hour later, he received a detailed reply from another user, Abu Hadafa, posted for all to see.
This kind of exchange is normally only read by committed radicals, but a proliferation of terrorist activity on social networking and video sharing sites means that other people are consuming their propaganda without realising it.
"If you are doing research and type 'Lebanon' or 'Gaza' in to YouTube, it's likely that you are watching a video that without being identified as such, was posted by Hizbollah or Hamas," said Dr Weimann.
Facebook is key for promoting links to videos and documents, he added. Once accepted in to somebody's group of online "friends", terrorists or terrorist-sympathisers can promote their propaganda, gather information on people, and sometimes also recruit.
A practical precaution that everyone can take, said Dr Weimann, is to be vigilant when receiving Facebook "friend requests", as terrorists make the most of the fact that many people automatically accept them without checking if they know the person.