Standard feature of Web browser design leaves opening for privacy attacks

December 04, 2000

Princeton, N.J. -- Princeton computer scientists have discovered a trait of Web browser design that allows Web sites to cull private information about the recent browsing histories of visitors.

While there is no evidence that any Web sites use such a snooping tactic, the researchers believe the method could pose serious risks to privacy. The technique is undetectable and defeats nearly all available privacy measures, although design changes in future browsers could reduce the problem.

Edward Felten, professor of computer science, and graduate student Michael Schneider described the technique in the proceedings of Association for Computing Machinery Conference on Computer and Communications Security, a major conference held Nov. 1-4 in Athens.

The researchers have dubbed the technique a "timing attack." It works by exploring the contents of the visiting browser's "cache" of recent activities, a log all browsers compile to increase their speed. In a timing attack, a Web site times how long it takes a browser to respond to queries about other sites. Company, for example, could test how quickly visiting browsers are able to access information from competitor's site. A quick response indicates that the Web user recently visited The test is very reliable, the researchers found.

Timing attacks could allow malicious Web site designers to create a more invasive form of Web "cookies," which are bits of data that Web sites store on visitors' browsers. Cookies are often used, for example, to allow a Web user to return to a password-restricted Web site without having to type in a password each time.

Felten and Schneider created a variation they call "cache cookies." Web sites could force a browser to store cache cookies without the permission required of normal cookies. (Web users have the option of instructing their browsers to reject conventional cookies.)

Any number of unrelated Web sites could then access these cache cookies and use them as a tool for learning whether a Web user has recently visited other Web sites. The scheme presents troubling opportunities to aggregate large amounts of information about Web users who do nothing more than visit sites.

"These qualities make cache cookies very dangerous to the privacy of Web users," the authors assert.

While no countermeasures would completely protect people from such invasion, the authors propose a method for redesigning browsers to prevent the majority of timing attacks. The redesign would employ a device called "domain tagging." It would allow information to be retrieved from the browser's cache of recently visited Web addresses only if the information pertains to the exact site the Web user is currently viewing.

Even that solution, however, is imperfect and does not prevent maliciously designed sites from inserting some forms of dummy addresses into a Web browser's cache and looking them up later.

Nonetheless, the researchers believe that domain tagging could work sufficiently well to assure Web users a reasonable level of privacy. "We think we understand what the solution is and we now are working to implement it," said Felten.

Felten said he felt compelled to publish a description of the potential problem to encourage positive discussion about resolving it. "We believed (timing attacks) would be discovered by other people before long and they would be used," he said. "You need to talk about a problem before it can be solved."

Princeton University

Related Privacy Articles from Brightsurf:

Yale team finds way to protect genetic privacy in research
In a new report, a team of Yale scientists has developed a way to protect people's private genetic information while preserving the benefits of a free exchange of functional genomics data between researchers.

Researchers simulate privacy leaks in functional genomics studies
In a study publishing November 12 in the journal Cell, a team of investigators demonstrates that it's possible to de-identify raw functional genomics data to ensure patient privacy.

Some children at higher risk of privacy violations from digital apps
While federal privacy laws prohibit digital platforms from storing and sharing children's personal information, those rules aren't always enforced, researchers find.

COVID-19 symptom tracker ensures privacy during isolation
An online COVID-19 symptom tracking tool developed by researchers at Georgetown University Medical Center ensures a person's confidentiality while being able to actively monitor their symptoms.

New research reveals privacy risks of home security cameras
An international study has used data from a major home Internet Protocol (IP) security camera provider to evaluate potential privacy risks for users.

Researcher develops tool to protect children's online privacy
A University of Texas at Dallas study of 100 mobile apps for kids found that 72 violated a federal law aimed at protecting children's online privacy.

Do COVID-19 apps protect your privacy?
Many mobile apps that track the spread of COVID-19 ask for personal data but don't indicate the information will be secure.

COVID-19 contact tracing apps: 8 privacy questions governments should ask
Imperial experts have posed eight privacy questions governments should consider when developing coronavirus contact tracing apps.

New security system to revolutionise communications privacy
A new uncrackable security system created by researchers at King Abdullah University of Science and Technology (KAUST), the University of St Andrews and the Center for Unconventional Processes of Sciences (CUP Sciences) is set to revolutionize communications privacy.

Mayo Clinic studies patient privacy in MRI research
Though identifying data typically are removed from medical image files before they are shared for research, a Mayo Clinic study finds that this may not be enough to protect patient privacy.

Read More: Privacy News and Privacy Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to