Facebook fined $US5 billion over privacy

Federal regulators are fining Facebook $US5 billion ($A4.47 billion) for privacy violations and instituting new oversight and restrictions on its business.

But they are only holding CEO Mark Zuckerberg personally responsible in a limited fashion.

The fine is the largest the Federal Trade Commission has levied on a tech company, although it won't much dent a company that had nearly $56 billion in revenue last year.

Zuckerberg must personally certify Facebook's compliance with its privacy programs. The FTC says false certifications could expose him to civil or criminal penalties.

Some experts thought the FTC might fine Zuckerberg directly or limit his authority over the company.

The commission opened their investigation after revelations that data mining firm Cambridge Analytica had gathered details on as many as 87 million Facebook users without their permission.