A lawyer has called on Facebook's one billion users worldwide to join a class action fight against the social network over privacy rights.
Austrian campaigner Max Schrems billed it as a David and Goliath lawsuit against the web giant claiming damages of 500 euro (£397) per supporter for alleged data protection violations, including over the US Prism spy programme.
In what could ultimately be the largest class and privacy action ever taken in Europe, angered users are being asked to sign up using an app on fbclaim.com.
"We are only claiming a small amount, as our primary objective is to ensure correct data protection," Mr Schrems said.
"However, if many thousands of people participate we would reach an amount that will have a serious impact on Facebook."
The lawsuit is being taken in the Commercial Court in Vienna against the Irish subsidiary of the New York-listed web giant.
Mr Schrems is moving his Europe-V-Facebook.org campaign from complaints to the Data Protection Commission in Ireland to the courts in his homeland as European consumer law allows for complainants to take legal actions where they live.
The privacy activist has more than 20 complaints of alleged data breaches involving Facebook filed with the Irish data watchdog.
The class action in Vienna claims Facebook Ireland is in breach of European law on users' data and that it violates rights by tracking internet use on external sites including the use of "like" buttons.
It also attacks Facebook's analysis of users through what it calls "big data" systems.
Mr Schrems claims the company supports the US Prism surveillance programme, the National Security Agency's secret monitoring and data mining exposed by whistleblower Edward Snowden.
An earlier landmark battle launched in Ireland to find out what Facebook tells US spy chiefs was referred to the European Court of Justice by a judge in Dublin last month.
Facebook declined to comment this morning.
Supporters have been urged to sign up on their smart phones and computers using the app and have been assured that there are no costs risks.
Mr Shcrems said he is the only claimant under the Austrian legal system while the action is being financed entirely by ROLAND ProzessFinanz AG. If it is successful, ROLAND will receive 20% of the damages for putting up the funding.
The class action is open to all registered adult Facebook users outside the US and Canada as users in all other countries have a contract with Facebook Ireland.
Arndt Eversberg, chief executive of ROLAND ProzessFinanz AG, said their role as a litigation funding company was not about Mr Schrems making a profit.
"Because of our long history as a litigation funding company we are used to levelling the playing field in the fight between David and Goliath. In this case it is particularly necessary," he said.
Mr Schrems added: "We love to complain constantly about data protection problems in Europe, now it's also time for us to enforce our fundamental rights.
"In the beginning we made great progress in Ireland. As a result of our complaints, Facebook had to delete data and deactivate its facial recognition all over the world."
Facebook has more than 1.3 billion users. Its shares are trading on the Nasdaq at around 72 US dollars, making it worth in the region of 200 billion US dollars (£118 billion).