The spy agency, with help from the U.S. National Security Agency, started a surveillance program called Optic Nerve that collected images from Yahoo web chats and saved them to bulk databases. And these interceptions were not limited to persons-of-interest; they involved data collection from possibly millions of individuals who were not intelligence targets.
The Guardian has secret documents, provided by NSA leaker Edward Snowden, that show the agency collected data from nearly 1.8 million Yahoo user accounts globally in a six-month period in 2008, including large amounts of sexually explicit communications.
When contacted by the Guardian, Yahoo was quick to deny any involvement with this data capture and denied any prior knowledge of the Optic Nerve program. The company even accused the agencies of "a whole new level of violation of our users' privacy."
"This report, if true, represents a whole new level of violation of our users' privacy that is completely unacceptable, and we strongly call on the world's governments to reform surveillance law consistent with the principles we outlined in December," said a spokesperson.
The documents say the Optic Nerve program began as a prototype in 2008 and was active until 2012. Rather than crowd their servers will the entire chat, the program would capture a still image from the chat every five minutes, partly to comply with human rights norms. The document also said these intercepts were "unselected" and not targeted at persons-of-interest.
The agency did, however, make efforts to limit these bulk searches to the metadata and tried to restrict the viewing of sexually explicit material by its agents, but does not go on to say if capturing such information was legal or not.
Optic Nerve captured information using GHCQ's large network of internet taps and then processed them using systems provided by the NSA. The information was fed into NSA's XKeyscore search tool, and NSA research was used to build the tool which identified Yahoo's webcam traffic.
The NSA refused to comment on the specifics of the story, however, NSA spokeswoman Vanee Vines said "As we've said before, the National Security Agency does not ask its foreign partners to undertake any intelligence activity that the US government would be legally prohibited from undertaking itself."
A GHCQ spokesman reiterated that all of its activities are in accordance with U.K. law and refused to comment on the specifics of any of its programs.
"Furthermore, all of GCHQ's work is carried out in accordance with a strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate, and that there is rigorous oversight, including from the secretary of state, the interception and intelligence services commissioners and the Parliamentary Intelligence and Security Committee," said the spokesman.