PALO ALTO (CBS/CNN) — Facebook said Wednesday that Cambridge Analytica, a data firm with ties to President Donald Trump’s campaign, may have had information on about 87 million Facebook users without the users’ knowledge.

Facebook had previously said the number of people whose information may have been shared with Cambridge Analytica was only around 50 million. It announced the revised number in a blog post on Wednesday.

Facebook has said the data was initially collected by a professor for academic purposes in line with its rules. The information was later transferred to third parties, including Cambridge Analytica, in violation of Facebook’s policies.

Starting next week, Facebook will tell people if their information was shared with Cambridge Analytica.

Facebook also said in the blog post Wednesday that “most people on Facebook” may have had their public profile information scraped by malicious actors. The people doing the scraping used account recovery and search tools that let users look people up by phone numbers and email addresses, then took information from profiles.

“Given the scale and sophistication of the activity we’ve seen, we believe most people on Facebook could have had their public profile scraped in this way,” said CTO Mike Schropfer in the post.

Rob D’Ovidio is an internet security expert and associate professor at Drexel University. He says it’s important to read the terms of service.

“They’ve taken steps to make it more user friendly,” said D’Ovidio.

Next, be wary of third-party apps like games, polls and quizzes since that’s how this breach began.

“Only a small amount of people filled out the quiz. Where the biggest vulnerability came was all the people connected to people who filled out quiz had their data used by this third party,” D’Ovidio said.

And finally, use your phone’s privacy settings to limit access until we learn more.

“So you can limit the ability of Facebook to access your camera, to access your photo library,” he says.

Facebook is turning off the search feature and changing how account recovery works. The blog post also outlines a number of other ways that Facebook is cracking down on third-party access to data.

The-CNN-Wire ™ & © 2018 Cable News Network, Inc., a Time Warner Company. All rights reserved.