Google Safe Browsing Feature Could Compromise Privacy

BLACK HAT USA, LAS VEGAS, NV -- Turns out a browser security extension from Google for Chrome and Firefox browsers can actually put user privacy at risk, according to a researcher here at the Black Hat USA conference.

Robert "RSnake" Hansen, CEO of SecTheory LLC, says he discovered that Google's Safe Browsing anti-phishing and anti-malware feature for Chrome and Firefox actually gathers and stores data about the user's machine and browsing habits that could potentially be abused by an attacker or even incriminate the user in a legal case.

"It's a time capsule on anyone who ever did anything in Chrome or Firefox ... they can be de-anonymized way after the fact, months or years after using those browsers and the settings are turned off," Hansen says.

Google basically stores a cookie on the user's computer that can be used to track him or her, he says. And the cookie can be used to identify the IP addresses he or she visits, for instance. Hansen says Google logs that data for anti-distributed denial-of-service (DDoS) purposes.

"If I'm the FBI and I say someone is hacking me at this physical location from this IP, I can issue a subpoena to Google to tell me other IP addresses associated with this," he says.

Hansen says because the cookie is stored locally and echoed out, the user's IP addresses get logged by Google. That information can be associated with their browsing history. "I'm not saying that browsing history [itself] is stored locally and echoed out," he says.

The bottom line, he says, is that the security features fall under the guise of providing anti-phishing and anti-malware, but gathering that information is "dangerous," he says. "Those lists are to track you as well as to protect you," he says.

"In Chrome, every five hours it phones home" to check for the current version and"sends a payload including machine ID and user ID," he says.

Mozilla, meanwhile, said it deploys Safe Browsing differently than Chrome does. Among other things, Firefox does fewer lookups with Google's servers because it downloads partial URL hashes that it checks locally. A Google spokesperson said that Chrome also checks hashes locally unless a match is found -- then it initiates a lookup on the server.

"If there is no match, Firefox does not do any further lookups with Google's servers at all, so there's zero network communication beyond the regular checks for database updates, and no information exchanged about where the user has been browsing," a Mozilla official said.

RSnake says Google's storing client-side information and sending it out to the Web is nice for tracking, he says, but doesn't make sense when it comes to privacy. "Ultimately, any time they store any kind of information on the browser and echo it back to the Internet, there is a potential leak of user's privacy."

The only way to protect your privacy from this, he says, is to turn off the anti-phishing and anti-malware options. "The bummer is you're turning off a great service," he says. "It protects you from malware" and other threats, he says.

"Everyone I've talked to has turned it [the Google service] off. They don't want to be tracked," he says.

Joshua "Jabra" Abraham, a security expert at Rapid7 who also demonstrated and released here some privacy hacking tools he developed, says the only way to protect yourself from your privacy being compromised is to disable the Safe Browsing feature, which is on automatically.

The researcher says he didn't talk to Google about the possible hack, but that Google would likely say it had no intention of using the features for that purpose. "But even if that's true, it's irrelevant," he says. "It just takes a subpoena from a government [agency] to get that information."

The good news, he says, is that Google only retains the data for two weeks, and then stores it in aggregate form. "But having this IP address, this cookie, and this timestamp is enough information to decloak someone for a [hacking] incident they did two years ago," he says. "So if you use Firefox or Chrome, you should know the risks" of the Safe Browsing feature, he says.

But a Google spokesperson said IP addresses and cookies are not combined with data from other services, nor used for tracking. "All such data is deleted after two weeks" and not anonymized, the spokesperson said.

Mozilla, meanwhile, says it has specific agreements with what Google can and cannot do with users' information. Third-party service providers such as Google can't use "any data or other information about or from users of Firefox for purposes other than to provide and maintain their service" nor can they "correlate any Firefox user data with any other data collected through other products, services or web properties of that provider," according to Mozilla's privacy policy.

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