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The Watch Ava Onlineinternet is a labyrinthian place, and Facebook is hiding around almost every corner. A new tool, dubbed Blacklight, helps you spot the behemoth lying in wait.

Developed and released by the Markup, Blacklight reveals what trackers are running in the background of websites without — and here's the key— you having to visit those websites first. One such tracker, the Facebook Pixel, is particularly problematic.

Facebook tracks users (and non-users), even when they're not logged in, via the Pixel. The Pixel is a largely unnoticeable "analytics tool" running in the background of millions of websites (including this one) which collates and reports your actions, on a granular level, back to Facebook. Among other things, the Pixel enables website owners to later target their visitors with ads on Facebook. In a recent test done by the Markup, 30 percent of popular websites were laden with an embedded Facebook Pixel.

"[The] pixel will fire when someone takes an action on your website," explains Facebook. "Examples of actions include adding an item to their shopping cart or making a purchase. The pixel receives these actions, or events, which you can view on your Facebook pixel page in Events Manager."

In other words, sites with Facebook Pixels are sending user data back to Facebook. Presumably, Facebook can then — as it does with information gleaned from Facebook's social plugins on third-party sites — tie this information to your Facebook account and, consequently, your real identity.

Why does this matter? Well, one site with the Facebook Pixel is WebMD. Ever searched for anything personal, or private, on WebMD?

"Our advertising service partners may use cookies and other tracking technologies to collect information about your use of the WebMD Sites, including content you have viewed," reads the WebMD privacy policy. "Two of the third parties that WebMD works with are Google and Facebook."

Thankfully, there are a few actions you can take to protect yourself against the Facebook Pixel. Facebook Container, for example, is an extension from Firefox that blocks Facebook trackers on non-Facebook sites. Use it.

Privacy Badger, from the Electronic Frontier Foundation, can identify tracking pixels, and uBlock Origin blocks all kinds of nefarious trackers, although we haven’t been able to confirm they specifically block Facebook Pixel.

More broadly, when you see a site that's using third-party tracking tools like the Facebook Pixel, you can reach out to the company behind the webpage directly to (politely) let them know that you object to their handing of your data over to Facebook. With enough complaints, the company might actually do something about it.

SEE ALSO: How to blur your house on Google Street View (and why you should)

Whatever you do, you should not simply resign yourself to the fact that Facebook knows — and will forever know — all of your browsing habits. Tools like Blacklight help make clear how pervasive Facebook's surveillance is, and, armed with that knowledge, empower you to push back.

Sunshine, after all, is a great disinfectant — even when coming from a digital blacklight.

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