Facebook is being sued by some 25,000 users for alleged violations of European privacy laws in a class action suit due in a Vienna court later.
The claim, led by Austrian data protection campaigner Max Schrems, focuses on the way Facebook collects and forwards data.
It has been brought against Facebook’s European headquarters in Dublin, which registers all accounts outside the US and Canada.
Facebook has not commented on the case.
More than 900 UK-based users of the site are involved in bringing the case.
The legal action also claims privacy laws are breached in the way the networking giant monitors users when they use the site’s “like” buttons.
Mr Schrems, a law graduate, wants to stop what he calls mass surveillance by the social networking site.
He also alleges the company co-operated with Prism, a surveillance system launched in 2007 by the US National Security Agency.
The case includes a compensation claim of about €500 ($539;£362) per person.
Mr Schrems has said that Facebook does not believe the case is admissible under Austrian law.
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Source:BBC