91av

Computer viruses often arrive as attachments to emails sent by automated servers or by PCs infected without the owner’s knowledge. And a new virus can slip through before you’ve had a chance to update the antivirus software. Lucent Technologies has patented a “reverse Turing test” that it hopes can plug the loophole (US 2003/204569). Lucent’s software looks for any suspicious incoming email and replies with an explanatory note and simple question, such as “What day is it today?” A human can easily reply accurately, but an infected machine cannot, allowing the software to isolate suspicious emails.