Moscow is adding facial-recognition technology to its network of 170,000 surveillance cameras across the city in a move to identify criminals and boost security. From a report: Since 2012, CCTV recordings have been held for five days after they're captured, with about 20 million hours of video stored at any one time. "We soon found it impossible to process such volumes of data by police officers alone," said Artem Ermolaev, head of the department of information technology in Moscow. "We needed an artificial intelligence to help find what we are looking for." Moscow says the city's centralized surveillance network is the world's largest of its kind. The U.K. is one of the most notorious for its use of CCTV cameras but precise figures are difficult to obtain. However, a 2013 report by the British Security Industry Association estimated there were as many as 70,000 cameras operated by the government across the nation.