A privacy lawsuit brought against Facebook by 25,000 people begins today, with the social network being accused of illegally tracking user data.
The class action case also alleges that the tech giant took part in the NSA's PRISM programme, which raked personal data from the servers of major US companies with their apparent agreement.
While Facebook denies any involvement, the claimants hope the case will improve tech companies' attitudes to data protection.
Campaigner Max Schrems said in an AFP interview: "We are asking Facebook to stop mass surveillance, to [have] a proper privacy policy that people can understand, but also to stop collecting data of people that are not even Facebook users.
"There is a wide number of issues in the lawsuit and we hope to kind of win all of them and to get a landmark case against US data-gathering companies."
Schrems claims Facebook has taken a "Wild West" approach to data protection, and the case concerns its treatment of non-US data stored on its Dublin servers.
The compensation requested by claimants - 360 per user adds up to 9 million.
Judges will decide whether Facebook is guilty of breaking EU law in its policy on data use, sharing data with external apps and tracking users on external pages, among other issues.
Facebook hasn't commented publicly on the case, but CEO Mark Zuckerberg denied any involvement in the NSA PRISM scheme back in 2013.
The campaign is being financed by litigation firm Roland Prozessfinanz and the company's 20 per cent fee will be deducted from the total damages awarded.
