Facebook is suing a South Korean firm it accuses of unlawfully using data to sell marketing and advertising, the BBC reports.
The social network is asking a judge to force Rankwave to allow it to audit the firm’s activities to see if user data was obtained and potentially sold.
A source at Facebook told the BBC it was as yet unable to say how much data or how many users may be affected.
The network said the move would “send a message to developers that Facebook is serious about enforcing our policies”.
“Facebook was investigating Rankwave’s data practices in relation to its advertising and marketing services,” said Jessica Romero, Facebook’s director of platform enforcement.
“Rankwave failed to co-operate with our efforts to verify their compliance with our policies, which we require of all developers using our platform.”
The BBC was unable to reach Rankwave for comment on Friday.