Australian police agencies are reportedly using a private, unaccountable facial recognition service that combines machine learning and wide-ranging data-gathering practices to identify members of the public from online photographs.

The service, Clearview AI, is like a reverse image search for faces. You upload an image of someone’s face and Clearview searches its database to find other images that contain the same face. It also tells you where the image was found, which might help you determine the name and other information about the person in the picture.

Clearview AI built this system by collecting several billion publicly available images from the web, including from social media sites such as Facebook and YouTube. Then they used machine learning to make a biometric template for each face and match those templates to the online sources of the images.

It was revealed in January that hundreds of US law enforcement agencies are using Clearview AI, starting a storm of discussion about the system’s privacy implications and the legality of the web-scraping used to build the database.

Australian police agencies initially denied they were using the service. The denial held until a list of Clearview AI’s customers was stolen and disseminated, revealing users from the Australian Federal Police as well as the state police in Queensland, Victoria and South Australia.