"Captcha (Completely Automated Public Turing test to tell Computers and Humans Apart) challenge-response systems, which are used to prevent accounts being created until a user correctly identifies letters in an image, are designed to ensure requests are made by a human rather than an automated program. The technique has been used to defeat automatic sign-ups…

"Mendacious machines controlled by hackers that reroute Internet traffic from infected computers to fraudulent Web sites are increasingly being used to launch attacks, according to a paper published this week by researchers with the Georgia Institute of Technology and Google Inc. The paper estimates roughly 68,000 servers on the Internet are returning malicious Domain Name…