Google's Invisibility Cloak

A percentage of Google traffic is stripped of identifying information. Why?

Google likes to portray itself as a company that does everything in the open. But it appears that at least some of its employees are harboring a secret.

Web researcher Net Applications recently discovered that between 11% to 30% of traffic streaming out of Google's (nasdaq: GOOG - news - people ) Mountain View, Calif., office is stripped clean of the usual identifying information that accompanies such traffic. That begs the question: What secret is it that Google doesn't want the rest of the Web to know?

The finding, first reported in InternetNews.com, quickly sparked online chatter about a Windows challenger in the works. "I'd be shocked if Google wasn't developing its own operating system," says Vince Vizzacarro, Net Applications' executive vice president of marketing. "They clearly want to ride online services without using Microsoft."

The Aliso Viejo, Calif.-based firm made the discovery after adding a new feature to its analytics software that pinpoints the source of Internet traffic down to a specific company. The technology, which tracks various trends in Internet usage by analyzing traffic to more than 40,000 Web sites around the world, can also detect a computer's browser, IP address, referring search engine or search term, default language and screen resolution.

The new data showed that a percentage of Internet users in Google's offices (principally based in the company's Mountain View headquarters) are using an operating system that essentially shields itself from detection by stripping traffic of identifying information. Vizzacarro describes this data, known as a user agent, as a string of information that a computer uses to identify itself. Removing it (possibly via a proxy server) means that outsiders like Net Applications can't tell which operating system a particular Web user is using. (Net Applications uses other methods, like a Web site's JavaScript to detect other information about a user and determine that the traffic is coming from Google.) About 11% of Google's Web traffic currently shows up like this. The level fluctuates daily, Vizzacarro says. A few days ago it was around 30%.

Traffic from Microsoft employees, in contrast, can be parsed in detail, leading some to wonder why Google is taking pains to cover its tracks. "It's not a natural process.

Google is the only company we've seen that does this," Vizzacarro says. Google employees not using the secret OS are employing various versions of Unix, such as Linux or Ubuntu, and some older operating systems, like X11, he says.