You could call it the attack of the clones. Major websites such as Yahoo Mail, Hotmail, Altavista and Ticketmaster are being inundated by malicious automated programs pretending to be humans.

The main objective of these programs or “bots” is to gain access to the websites’ services and send spam, harass users, gather personal information or hog resources.

To ward off these bots, webmasters are increasingly turning to a technology called Captcha, an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart.