According to Belgian counter-terrorism sources, the trigger for the Brussels arrests was an intercepted e-mail sent by one of the alleged recruits, Beyayo, in early December shortly after he returned to Belgium.

CNN: Recruits reveal al Qaeda's sprawling web

According to Belgian counter-terrorism sources, the trigger for the Brussels arrests was an intercepted e-mail sent by one of the alleged recruits, Hicham Beyayo, in early December shortly after he returned to Belgium.

CNN: Al Qaeda priority: Western targets

To counter this, Chinese activists are returning to older, decentralised, internet services such as e-mail and chat rooms.

ECONOMIST: The internet and government