It might not be a person who knows us best, but instead our computers, thanks to the digital crumbs of seemingly innocent personal information many of us put online.
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Digital Shadow, a promotion for the Ubisoft game called "Watch Dogs," which comes out later this month, scrapes consenting users' Facebook profiles and prepares a dossier of private information about them that is eerily accurate.
"We collectively are being scraped all day everyday. Not just by Facebook, but by virtually every website we visit via our browser and the various website technologies that we have built in," Robert Siciliano, an identity theft expert with McAfee, told ABCNews.com.
"What you're seeing here is a collective of a variety of tech all harnessed into this stunt that provides a transparent look of what's going on behind the scenes," he said.
Digital Shadow pulls from your tagged photos, even boasting: "We know who you are."
It also knows who a user cares about the most.
I exhibit a “high level of interaction” with my sister and my best friend from home. My “stalkers” are listed –- these are people who interact heavily on my profile. A few friends, my Aunt Carol, my kindergarten teacher who clicks "like" on every article I post.
The site also knows the friends I interact with the most. Finally, it lists my “liabilities.” These are all people who consistently tag me in photos and posts, thus exposing my data and making me even more identifiable to Facebook.
They also know where to find me logged on at ABC News' New York office. To make it extra creepy, they even posted a Google Maps photo of the building.
The site also knows how many photos I have posted and how many friends I have on Facebook.
"If you don't want data collected on you, that means abstaining from social media," Siciliano said.
If a world without Facebook and other social media seems impossible, Siciliano recommends being smart about the data you share and "reverse engineering" how it could be used against you.
Siciliano is a fan of his favorite ice cream brand on Facebook, but said he knows better than to be baited into clicking on any potential coupons that could install malware on his computer.
Other ways users can minimize their digital shadow, according to Siciliano, include:
"These are the things you do if you really want to hide," Siciliano said. "But this is what I tell people: 'Ask yourself, what harm can come from your data?'"