The so-called "Perspectives" system will also protect against attacks on Domain Name System software, Carnegie Mellon University researchers said in a press release. Their protective software is available for free download as an extension for the Mozilla Firefox v3 browser at www.cs.cmu.edu/~perspectives/firefox.html.

"It's very, very, very easy for someone to convince you to go through their computer" when making connections through public WiFi, said David Andersen, assistant professor of computer science. A user who thinks he is linked to an airport or coffee shop "hot spot," for instance, might actually be linked to a laptop of someone just a few seats away. "A lot of people wouldn't even know they've been attacked," he added.

The Perspectives system is designed to aid in authenticating Web sites for financial services, online retailers and other transactions needing secure communications. By independently querying the desired site, the system can double check whether each is receiving the correct authentication information, called a digital certificate.