A proposed class-action lawsuit claims that Google has been tracking users even when Chrome is set for private browsing. The lawsuit is seeking at least $5 billion in damages.

“Google tracks and collects consumer browsing history and other web activity data no matter what safeguards consumers undertake to protect their data privacy,” the complaint explains. “Indeed, even when Google users launch a web browser with ‘private browsing mode’ activated (as Google recommends to users wishing to browse the web privately), Google nevertheless tracks the users’ browsing data and other identifying information.”

Surprisingly, Google achieves this tracking in part via Chrome’s secret advertising-related functionality.

“When an internet user visits a webpage or opens an app that uses … Google Analytics, Google Ad Manager, … [or] the ‘Google Sign-In button’ for websites (over 70% of all online publishers use such a service), Google receives detailed, personal information such as the user’s IP address (which may provide geographic information), what the user is viewing, what the user last viewed, and details about the user’s hardware,” the complaint continues. “Google takes the data regardless of whether the user actually clicks on a Google-supported advertisement—or even knows of its existence. This means that billions of times a day, Google causes computers around the world to report the real-time internet communications of hundreds of millions of people to Google.”

As the complaint notes, Google’s tracking is a serious violation of privacy and because it’s done secretly, it’s also deceptive to consumers and is both intentional and unlawful. “Federal privacy laws prohibit unauthorized interception, access, and use of the contents in electronic communications, the suit explains.

Because there are likely millions of people impacted—this is just in the United States, as Chrome’s worldwide usage is in the billions—the plaintiffs are seeking class-action status. They are also seeking $5000 in damages per user.

Google has quickly denied the charges, which come amidst heightened antitrust scrutiny of the firm and its biggest rivals.

“We strongly dispute these claims, and we will defend ourselves vigorously against them,” a Google statement reads. “Incognito mode in Chrome gives you the choice to browse the internet without your activity being saved to your browser or device. As we clearly state each time you open a new incognito tab, websites might be able to collect information about your browsing activity during your session.”