According to documents leaked by Edward Snowden to the British newspaper the Guardian, millions of Yahoo webcam chats have been intercepted by British security agency GCHQ (Government Communications Headquarters) using systems developed by the NSA. 

The documents reveal British intelligence used a software program called Optic Nerve to intercept, at random, at least 1.8 million Yahoo video chats across the globe. The program was used to essentially run a giant experiment: still images were taken from the chats, stored, and run through facial recognition software that would try to find matches with targets. 

The revelations raise questions about other web chat services, says Chris Green, an analyst with Davies Murphy Group. “If they’ve been doing this with Yahoo it puts into focus all the other services that make use of webcam anything from skype to facetime.”

Up to 11% of the images were of a sexual nature, though access to photos by intelligence analysts was allegedly limited to when a suspected match was made. Green says U.S. and British agencies have an advantage in collecting this type of data, because “it’s commonplace for organizations, particularly in the U.S., that for encryption over a certain level, keys have to be shared with the government on the grounds of national security.” 

That doesn’t mean that Yahoo knew about this particular program, the company reacted with fury to the news, calling it a “whole new level of violation” of its users.