Next year the Janus program, an initiative run by the director of national intelligence, will begin to collect photographs of people’s faces from social media websites and public video feeds. Machines will then use powerful algorithms to pair those photos with existing biometric profiles.

The Janus program isn’t alone: Facial-recognition technology is quickly becoming a mainstay of commercial and government surveillance systems. While it can provide benefits in automation and security, it is also a threat to privacy. Sophisticated algorithms can already extract information about your gender, age and even mood from a single image, and then link those physical attributes to commercial or government databases.