Websites ‘Leaking’ User Info To Other Firms

Many top websites share their visitors’ names, usernames or other personal information with their partners without alerting users and, in some cases, without knowing they’re doing it, according to a new study from Stanford University.

Many websites “leak” usernames to third-party advertising networks by including usernames in URLs that the ad networks can see in referrer headers, said the study, released Tuesday by Stanford Law School’s Center for Internet and Society. While there’s a debate in legal circles whether usernames are personal information, there’s a growing consensus among computer scientists that Web-based companies can use usernames to identify their owners, said Jonathan Mayer, a Stanford graduate student who led the study.

“The vast majority of usernames are unique,” he said. “Given the prevalence of social networking, often times, once you have a username for a social network, you then also have a person’s real name, possibly a photo, possibly more.”

Other websites share first names, email addresses and other information with advertising or other partners, Mayer said at a privacy conference in Washington. Those identifiers “get associated not just with what you’re doing right now, but get associated with what you’ve done in the past, and what Web browsing activity you may have in the future,” he said.

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