Privacy experts have described as “very dangerous” revelations an Australian entrepreneur has developed facial recognition technology that is being used by US law enforcement agencies, allowing surveillance images to identify suspects by matching their social media profiles.

The New York Times reported on Sunday that Hoan Ton-That - an Australian developer and one-time model - has developed a facial recognition app that allows a user to take a picture of a person, upload it and get to see public photos of that person along with links to where those photos appeared. It noted the development may “end privacy as we know it”.

Hoan Ton-That, whose app matches faces to images it collects from across the internet. Credit:Amr Alfiky/The New York Times

Police in the state of Indiana reportedly solved a case within 20 minutes of using the app. After a bystander recorded a fight that ended when one shot the other in the stomach, police ran a still of the gunman's face through the app. They got a match: the man appeared in a video posted on social media, and his name was included in a caption on the video.

The system developed by Clearview AI uses a database of more than three billion images that the company claims to have scraped from user uploaded images and videos to social media including Facebook and YouTube.