Of course they've been doing this:
The National Security Agency is harvesting huge numbers of images of people from communications that it intercepts through its global surveillance operations for use in sophisticated facial recognition programs...
The NSA is harvesting millions of people's images from the Internet, particularly Facebook, various social media, and "unidentified" other sources to feed into its very sophisticated facial recognition technology and then matching them up with its troves of intercepted communications, according to the latest release from the Snowden documents.
The spy agency’s reliance on facial recognition technology has grown significantly over the last four years as the agency has turned to new software to exploit the flood of images included in emails, text messages, social media, videoconferences and other communications, the N.S.A. documents reveal....
The agency intercepts “millions of images per day” — including about 55,000 “facial recognition quality images” — which translate into “tremendous untapped potential,” according to 2011 documents obtained from the former agency contractor Edward J. Snowden. While once focused on written and oral communications, the N.S.A. now considers facial images, fingerprints and other identifiers just as important to its mission of tracking suspected terrorists and other intelligence targets, the documents show.
Because of course The Terrorists are busy posting pix of themselves on Facebook and connecting up with all their dangerous friends that way.
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This part is handy for them - it's perfectly legal. (Or maybe not, since they're not sharing what their actual sources are for these images.)
It is not clear how many people around the world, and how many Americans, might have been caught up in the effort. Neither federal privacy laws nor the nation’s surveillance laws provide specific protections for facial images....
Because the agency considers images a form of communications content, the N.S.A. would be required to get court approval for imagery of Americans collected through its surveillance programs, just as it must to read their emails or eavesdrop on their phone conversations, according to an N.S.A. spokeswoman.
State and local law enforcement already use databases of facial imagery, including driver’s licenses and images gleaned from social media. The FBI is developing methods to combine its automated fingerprint identification with facial imagery and other biometric data. The State Department has its huge database of passport photos and visa applicants. Supposedly the NSA has access to none of these.
The agency’s use of facial recognition technology goes far beyond one program previously reported by The Guardian, which disclosed that the N.S.A. and its British counterpart, General Communications Headquarters, have jointly intercepted webcam images, including sexually explicit material, from Yahoo users.
The N.S.A. achieved a technical breakthrough in 2010 when analysts first matched images collected separately in two databases — one in a huge N.S.A. database code-named Pinwale, and another in the government’s main terrorist watch list database.... That ability to cross-reference images has led to an explosion of analytical uses inside the agency. The agency has created teams of “identity intelligence” analysts who work to combine the facial images with other records about individuals to develop comprehensive portraits of intelligence targets.
The agency has developed sophisticated ways to integrate facial recognition programs with a wide range of other databases. It intercepts video teleconferences to obtain facial imagery, gathers airline passenger data and collects photographs from national identity card databases created by foreign countries....
The government is developing the intrusive technology that makes this invasion of privacy possible. The private sector is jumping on all the commercial exploitation possibilites. At what point is there some recogntion that your image and biometric data belong to you in the same way your DNA does, and should not be allowed to be exploited against your will and against your own interests?
N.S.A. Collecting Millions of Faces From Web Images