Browsers' private modes leak info, say researchers

And here's a shocker: private browsing often used for porn, not gift-buying

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Nor would Jackson name the browser that he and the other researchers believed is best at keeping secrets from others, or other sites. Every browser leaks some information, he noted, and every browser has flaws to fix.

"This is an important feature for users to have, and the fact that it's not perfect is no reason to avoid using it on the Web," said Jackson.

Jackson and the others -- Gaurav Aggarwal, Elie Burzstein and Dan Boneh, all at Stanford -- ran other tests to determine when and for what purpose people used private browsing. Some of the results were surprising, said Jackson; others were not.

Of the latter, their research confirmed what most suspect: Private browsing is used more often when users surf to adult-oriented sites than when visiting gift-buying or news sites. "This observation suggests that some browser vendors may be mischaracterizing the primary use of the feature when they describe it as a tool for buying surprise gifts," the four researchers said in their paper.

Microsoft still uses that gift-buying scenario in its promotional copy for IE8's InPrivate mode. For obvious reasons, browser makers have been reluctant to acknowledge what most users see as the feature's primary purpose -- hiding their surfing of adult sites -- a perception that produced the tongue-in-cheek "porn mode" label for the tool.

More surprising, said Jackson, was that Safari and Firefox users run in private mode more than people using either IE or Chrome. According to the tests, Safari users were twice as likely to run in private mode than Chrome users, and nearly seven times more likely than people using IE.

"I was a little bit surprised at that," Jackson said.

But the researchers had an explanation. "We found that private browsing was more commonly used in browsers that displayed subtle private browsing indicators," their paper stated, pointing out that Safari and Firefox display private browsing mode less prominently than Chrome and IE.

To Jackson, that meant Safari and Firefox users had probably forgotten that they were in private mode, and had simply neglected to turn it off.

The research paper authored by Jackson, Aggarwal, Burzstein and Boneh can be downloaded from the Stanford University site (download PDF).

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@ix.netcom.com.

Copyright © 2010 IDG Communications, Inc.

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