Is Facebook's 'Like' button spying on you?

The ubiquitous Facebook "Like" and Twitter "Tweet" buttons let web users share content with their friends and followers, but, unbeknownst to most, they also let the social-media sites track users — even when people don't click on them, according to a study done for The Wall Street Journal. Here, a guide to the buttons and the privacy concerns they raise:

What do these buttons do?

Their primary function is to let users share items from across the web with their social networks. But they also place "cookies" on a user's computer that allow Facebook and Twitter to know when a user visits a specific page. If you visit any web page with a "Like" button on it (like this one), Facebook knows about it. And the buttons "could link users' browsing habits to their social-networking profile, which often contains their name," says Amir Efrati in The Wall Street Journal.

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And it tracks you even if you don't click the buttons?

Yes. As long as you've logged into Facebook or Twitter once in the past month, your data is collected, even if you don't click the button. The tracking stops only when a user "explicitly logs out of their Facebook or Twitter accounts," says Efrati in the Journal.

How common are these widgets now?

The Facebook and Twitter buttons "have been added to millions of web pages in the past year," says Efrati. Facebook's widget appears on one-third of the 1,000 most-visited websites in the world, while buttons from Google and Twitter are on one-quarter and one-fifth of those sites, respectively.

Is Facebook using this data?

Facebook, Twitter, Google, and other "widget-makers" say they don't use the data to track users. And they say that the data is "anonymized" so that it can't be traced back to specific users. Facebook says it only uses the data to power targeted ads. The social network stores the data for three months, which is "substantially longer than the two weeks Google stores similar information," says Lee Mathews at Geek.com. Twitter says it doesn't use the data and deletes it "quickly."

What can be done to minimize this tracking?

"If you’re worried" about it, you should "log out of these sites after you’re done checking your email, tweeting, poking, or what have you," says Kashmir Hill in Forbes. "Yeah, you'll have to re-enter your password more often," says Linda Sharps at The Stir, "but it seems like you can have either convenience or privacy these days — not both."

Sources: Forbes, Geek.com, Newser, The Stir, Wall Street Journal