Schneier - Identifying a Person Based on a Photo, LinkedIn and Etsy Profiles, and Other Internet Bread Crumbs

Interesting story of how the police can identify someone by following the evidence chain from website to website.

According to filings in Blumenthal's case, FBI agents had little more to go on when they started their investigation than the news helicopter footage of the woman setting the police car ablaze as it was broadcast live May 30.

It showed the woman, in flame-retardant gloves, grabbing a burning piece of a police barricade that had already been used to set one squad car on fire and tossing it into the police SUV parked nearby. Within seconds, that car was also engulfed in flames.

Investigators discovered other images depicting the same scene on Instagram and the video sharing website Vimeo. Those allowed agents to zoom in and identify a stylized tattoo of a peace sign on the woman's right forearm.

Scouring other images ­-- including a cache of roughly 500 photos of the Philly protest shared by an amateur photographer ­-- agents found shots of a woman with the same tattoo that gave a clear depiction of the slogan on her T-shirt.

[...]

That shirt, agents said, was found to have been sold only in one location: a shop on Etsy, the online marketplace for crafters, purveyors of custom-made clothing and jewelry, and other collectibles....

The top review on her page, dated just six days before the protest, was from a user identifying herself as "Xx Mv," who listed her location as Philadelphia and her username as "alleycatlore."

A Google search of that handle led agents to an account on Poshmark, the mobile fashion marketplace, with a user handle "lore-elisabeth." And subsequent searches for that name turned up Blumenthal's LinkedIn profile, where she identifies herself as a graduate of William Penn Charter School and several yoga and massage therapy training centers.

From there, they located Blumenthal's Jenkintown massage studio and its website, which featured videos demonstrating her at work. On her forearm, agents discovered, was the same distinctive tattoo that investigators first identified on the arsonist in the original TV video.

The obvious moral isn't a new one: don't have a distinctive tattoo. But more interesting is how different pieces of evidence can be strung together in order to identify someone. This particular chain was put together manually, but expect machine learning techniques to be able to do this sort of thing automatically -- and for organizations like the NSA to implement them on a broad scale.

Another article did a more detailed analysis, and concludes that the Etsy review was the linchpin.

Note to commenters: political commentary on the protesters or protests will be deleted. There are many other forums on the Internet to discuss that.

from Schneier on Security https://www.schneier.com/blog/archives/2020/06/identifying_a_p.html