Taylor Swift reportedly used facial recognition technology at her live concert to identify stalkers.

According to a report in Rolling Stone, at a May 18 concert at the Rose Bowl in California, a facial recognition camera was installed inside a kiosk which displayed Swift’s rehearsal footage.

How does it work?

The camera reportedly took photos of anyone who stopped to take a look, subsequently sending them to a “command post” in Nashville, Tennessee. So, technicians there check them against a database of her stalkers.

The report comes amid privacy concerns stemming from facial recognition technology.

One recent example being Secret Service plans to deploy facial recognition in and around the White House. However, the American Civil Liberties Union (ACLU) said it captured outsiders as well.

In May, Amazon came under scrutiny following an ACLU reveal; that Amazon sold its facial recognition software to law enforcement agencies.

Here’s what Steve Knopper at Rolling Stone said:

Taylor Swift fans mesmerized by rehearsal clips on a kiosk at her May 18th Rose Bowl show were unaware of one crucial detail:

A facial-recognition camera inside the display was taking their photos.

Despite the obvious privacy concerns — for starters, who owns those pictures of concertgoers and how long can they be kept on file? — the use of facial-recognition technology is on the rise at stadiums and arenas, and security is not the only goal.

A representative for Swift didn’t immediately respond to a request for comment.