Facebook may be tracking your actions online even after you log off from the social networking site, according to a class-action lawsuit filed by two high-powered law firms.

The complaint alleges that Facebook installed cookies—tiny files that allow websites to remember user preferences, browsing data, and more—on users' computers that continued to track their Internet use after they'd left Facebook.

That doesn't jibe with Facebook's terms of use, which state that "when you log out of Facebook, we remove the cookies that identify your particular account." It also may violate the Federal Wiretap Act and Stored Electronic Communications Act, according to the official complaint.

In late 2011, Facebook acknowledged that a programming bug resulted in cookies not being deleted from users' computers, but said it never used the data gleaned from those cookies. But in February 2011, Facebook filed an application with the United States patent office that would give the company a method "for tracking information about the activities of users of a social networking system while on another domain."

In January, Congressman Joe Barton said the company's moves were confusing. "Facebook seems to be saying one thing and doing another," he said. Facebook "talks a lot about how they don't currently 'track' users online, but they just asked for a patent that would allow them to do just that. Why ask for something you don't ever plan on using?"

A spokesperson for Facebook wrote in an email that the company believes the case will be thrown out.

"We believe that this case is without merit and we will fight it vigorously," he said.

The complaint seeks statutory and punitive damages for a class of possibly more than 100 million American Facebook users.

William Murphy Jr., founding partner of one of the firms filing the complaint, said in a statement that the "days when online service providers can run roughshod over the privacy rights of their customers are over."