Facebook has shared users' private messages, contact information and other personal data with companies such as Microsoft and Spotify, according to a New York Times report that was alarming even in light of previous disclosures about the social network's practices.
Is there anything users can do to protect their data without walking away from Facebook altogether?
Experts say there is not much you can do about information that is already in Facebook's hands. But you can at least find out what the company has on you, and you can take steps to limit how much more it can gather from here on in.
Review privacy settings: Facebook claims it had permission to give companies the data outlined in the Times story, though the company tends to define "permission" loosely.
Users can at least employ their privacy settings to try to limit access as much as possible. Facebook offers a series of shortcuts.
On desktops and laptops, look for the triangle on the upper right corner of the browser. On Apple and Android devices, you can access shortcuts through the menu, denoted by three horizontal bars. Select "settings" and "privacy" to review who has access.
You can limit who sees your posts and other activity, turn off your location history, and disable third-party apps from having access to your data, although again, some of the information that Facebook shared was supposedly private.
You can also change other privacy settings by checking "Timeline and Tagging" in your account settings.
Read the terms of service: Facebook says it didn't violate user agreements in sharing the data. Whether that's true or not, most users barely even look at terms of service notifications before clicking "accept."
Reading through one can be dizzying. But it can illuminate just how much access Facebook has to your data and can give users a glimpse of what's going on behind the scenes.
Of course, Facebook can change the agreement at any time, said Rich Mogull, CEO of data security firm Securosis, so it can be hard to determine whether Facebook is violating any terms or not. That's on purpose, he says.
"Look how long the agreement is," he said. "It's written by the best-paid lawyers in the world."
Minimize your Facebook presence: Tim Bajarin, president of consultancy Creative Strategies, says in light of the recent news on what Facebook is doing, he has changed the way he uses the service. While he used to share photos of family, now "it's mostly dogs and cats," he said.
Experts advise that if you are worried about what Facebook does with your data, limit your time on the service and minimize posting. Essentially, assume all information you share is public, regardless of any privacy settings. Also, avoid clicking on any ads or posts; that will limit Facebook's access to your data.
Find out what Facebook knows: Even if you can't stop Facebook altogether from using your data, you can at least take a look at what it has on you. And it is probably a lot. Facebook allows people to download all of their data that the company has collected.
Under "Settings," click on "Your Facebook Information" and "Download Your Information." You will get a file with every photo and comment you've posted, all the ads you've clicked on, stuff you've liked and searched for, and everyone you've friended — and unfriended — over the years.
Evaluate your relationship with Facebook: Ultimately, whether you stay on Facebook depends on how much the service benefits you versus how much it takes from you.
Bajarin said connecting with friends and family is still worth the risk of sharing his data. "But I'm becoming more targeted about who I communicate with, and I'm taking more control of what I post and what I don't post," he said.
Mogull said users have to determine for themselves whether it is worth it to stick with Facebook. Because of the way Facebook makes money — using extensive user data to sell advertisers finely targeted ads — "your best interest is not in Facebook's best interest," he said.