(ABC NEWS)- To get an idea of the data Facebook collects about you, just ask for it. You'll 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.
This trove of data is used to decide which ads to show you. It also makes using Facebook more seamless and enjoyable — say, by determining which posts to emphasize in your feed, or reminding you of friends' birthdays.
Facebook's privacy practices have come under fire after a Trump-affiliated political consulting firm, Cambridge Analytica, got data inappropriately from millions of Facebook users. While past privacy debacles have centered on what marketers gather on users, the stakes are higher this time because the firm is alleged to have created psychological profiles to influence how people vote or even think about politics and society.
You can turn off ad targeting and see generic ads instead, the way you would on television or in a newspaper. In the ad settings, you'd need to uncheck all your interests, interactions with companies and websites and other personal information you don't want to use in targeting. Of course, if you click on a new interest after this, you'll have to go back and uncheck it in your ad preferences to prevent targeting. It's a tedious task.
As Facebook explains, it puts you in target categories based on your activity. So, if you are 35, live in Seattle and have liked an outdoor adventure page, Facebook may show you an ad for a mountain bike shop in your area.
And, increasingly, Facebook tries to match what it knows about you with your offline data, purchased from data brokers or gathered in other ways. The more information it has, the fuller the picture of you it can offer to advertisers. It can infer things about you that you had no intention of sharing — anything from your ethnicity to personality traits, happiness and use of addictive substances, Tufekci said.
These types of data collection aren't necessarily explicit in privacy policies or settings.
Facebook has since restricted the amount of types of data apps can access. But other types of data collection are still permitted. For this reason, it's a good idea to check all the apps you've given permissions to over the years. You can also do this in your settings.