"The content of messages between people is not used for ads targeting", a company spokesperson said.
The social media giant, however, did not reveal the identity or locations of these 335 users.
The Federal Trade Commission also is probing whether Facebook violated a 2011 consent agreement to protect privacy after data from as many as 87 million users, most in the USA, were shared with political consulting firm Cambridge Analytica. Concerns over Facebook data privacy may prompt regulation " Zucker can't be trusted, oversight, oversight", chanted a handful of protesters outside the Facebook "like" sign.
The investigation comes as Italian consumer advocate group Codacons prepares a USA class action against Facebook on behalf of Italians whose data was mined by Cambridge Analytica.
The tool was discovered by TechCrunch, which noticed a discrepancy between emailed receipts of Facebook messages being received (which Facebook can not retract) and the actual contents of Facebook inboxes. We want to make sure Page information is only available to apps providing useful services to our community. Now, future access to the Pages API will need to be approved. Apps will no longer be able to access the member list of a group.
Meanwhile Facebook will be accelerating the deprecation of Instagram API Platform, disabling all remaining capabilities to read public media on a user's behalf and reading a user's own profile info and media.
In a rare interview conference call with journalists (including this one) the other night, Facebook boss Mark Zuckerberg admitted that both he and his company have consistently gotten it wrong when it comes to assessing the damage that is being done by those manipulating Facebook. They gave us assurances and it wasn't until other people told us it wasn't true ...
Private data of over 5.6 lakh Indian Facebook users was compromised by a private marketing firm that later sold the personal details acquired through a quiz app to Cambridge Analytica, a UK-based company at the centre of a global privacy breach storm.
Zuckerberg accepted responsibility this week for the failure to protect user data but maintained he was still the best person to lead the network of two billion users.
"We realise we won't catch every ad that should be labelled, and we encourage anyone who sees an unlabelled political ad to report it. People can do this by tapping the three dots at the top right corner of the ad and selecting Report Ad", it said.