07/29/2010 12:42 pm ET | Updated May 25, 2011

'Private' Browsing Sessions Not As Private As You Think

Surfing the Internet with a web browser's "private mode" enabled may not keep users' information as safe as they think, Switched reports, citing research conducted at Carnegie Mellon University.

Carnegie Mellon's Collin Jackson told New Scientist that some sites may leave data on a computer's hard drive, even if they were accessed while private browsing was enabled, effectively providing traces of what sites you've visited.

As Jackson and his team note, "sites visited while browsing in private mode should leave no trace on the user's computer." And yet, Jackson tells New Scientist that a hacker could "guess what sites you've been to based on traces left behind." Switched summarizes the dilemma: "when your average surfer turns on the private mode in a browser, they expect their tracks to be erased, and erased they're not."

For example, an online banking website may store users' personal security keys on their PCs. By leaving information--even during a "private" visit--websites violate safety criteria established by Jackson and his research partners in their report.

While the research sheds new light on the limits of "private browsing," Rik Ferguson a UK-based security researcher at Trend Micro Internet Security counters that, "If someone is capable of tracking your browsing habits in this way, then they are probably also tech-savvy enough to know about commercial spyware which could much more effectively track your computer use."