http://www.theregister.co.uk/2004/08/02/al_qaeda_cyber_terror_panic/
Thomas C Greene
"The New York Times claims that Khan had 'told investigators that most of al-Qaeda's communications were now done through the Internet, the official said. After a message was sent and read by the recipient, the entire communication and related files were deleted to maintain secrecy, he said. Mr. Khan had told investigators that e-mail addresses were generally not used more than a few times.'"
