Facebook was sued over allegations it systematically intercepts its users private messages on the social network and profits by sharing the data with advertisers and marketers.

When users compose messages that include links to a third- party website, Facebook scans the content of the message, follows the link and searches for information to profile the message-sender's Web activity, violating the Electronic Communications Privacy Act and California privacy and unfair competition laws, according to the suit.

The practice compromises privacy and undermines Facebook's promise of "unprecedented" security options for its messaging function, two Facebook users said in the complaint filed in federal court in San Jose.

Lawsuits against Internet companies and social networks are multiplying as use of the Web balloons and users become more aware of how much personal information they're revealing, often without their knowledge. Google (GOOG), Yahoo (YHOO) and LinkedIn also are facing accusations of intercepting communications for their profit at the expense of users or non-users.

The scanning "is a mechanism for Facebook to surreptitiously gather data in an effort to improve its marketing algorithms and increase its ability to profit from data about Facebook users," Michael Sobol, an attorney for the plaintiffs, wrote in the Dec. 30 complaint.

Jackie Rooney, a spokeswoman for Facebook, said the company regards the allegations as "without merit."

The plaintiffs are seeking a court order certifying the case as a group, or class action, lawsuit on behalf of all Facebook users who have sent or received a private message in the past two years that included a Web links. They are also asking to bar Facebook from continuing to intercept messages and seek as much as $10,000 in damages for each user.