E-mail which may be infected by a computer virus is advantageously filtered by incorporating a "Reverse Turing Test" to verify that the source of a potentially infected e-mail is human and not a machine, and that the message was intentionally transmitted by the apparent sender. Such a test may, for example,...http://www.google.com/patents/US20030204569?utm_source=gb-gplus-sharePatent US20030204569 - Method and apparatus for filtering e-mail infected with a previously unidentified computer virus
