The FBI is tracing a digital trail to Capitol rioters

Capitol rioters, eager to share proof of their efforts with other extremists online, have so far left a digital footprint of at least 140,000 images that is making it easier for federal law enforcement officials to capture and arrest them.

The big picture: Law enforcement's use of digital tracing isn't new, and has long been at the center of fierce battles over privacy and civil liberties. The Capitol siege is opening a fresh front in that debate.

Between the lines: A huge part of the recruitment process for both foreign and domestic terrorists is capturing imagery of foul play and using it later to recruit new members. But advances in technology make it easy for perpetrators to accidentally out themselves to law enforcement in the process.

Details: In a report issued Friday, FBI Washington Field Office Assistant Director in Charge Steven M. D’Antuono said the FBI has so far identified more than 270 suspects involved in criminal activity in and around the Capitol, in large part thanks to incoming tips that help match pictures and videos uploaded online from the attacks.

• "In the past week alone, we’ve received nearly 140,000 photos and videos from the public," he said. The FBI has now set up a portal for people to submit tips about who may have been involved in the attacks, and who may be plotting more.

Evidence piling up: There are dozens of instances of people posting themselves on social media invading the Capitol or being spotted on video later, leading to arrests.

• Edward Jacob Lang, 25, posted multiple videos and photos of himself at the Capitol and was charged with assault for attacking a police officer with a bat.
• Brandon Fellows, 26, posted himself on Snapchat sitting at Democratic Senator Jeff Merkley’s desk and was charged with trespassing and disorderly conduct.
• Nicholas Moncada, 20, posted himself on Instagram from inside the Capitol and was arrested after college classmates tipped off the FBI.

It's not just selfies, of course. Other photos and videos from the siege have circulated widely and helped lead to arrests.

• Video evidence of Peter Francis Stager, 41, shows him using an American flag to beat a DC police officer.
• Robert Lee Sanford, 55, was caught on video throwing a fire extinguisher at Capitol Police.
• Richard Barnett, 60, was arrested after posing for a photo lounging at a desk in House Speaker Nancy Pelosi’s office.

Be smart: The feds aren't saying so far whether any arrests or investigations have been helped along by facial recognition. The technology could prove valuable in fingering yet-to-be-identified rioters, but it raises serious concerns about privacy, ethics and accuracy.

• Searches from controversial artificial intelligence firm Clearview AI searches have spiked 26% in the days following the Capitol riot, according to CNET. 
• The FBI’s use of facial recognition to surveil Black Lives Matters protesters last summer drew outrage.

Yes, but: Some researchers, per Protocol, worry that outing rioters publicly via their social media uploads could also have a damaging effect, especially if they are wrongfully accused.