Thumbs up, or thumbs down: that's the option presented to analysts when the tool Giant Oak Search Technology surfaces content from social media and other sources for ICE to scrutinize.

Immigration and Customs Enforcement (ICE) has used a system called Giant Oak Search Technology (GOST) to help the agency scrutinize social media posts, determine if they are “derogatory” to the U.S., and then use that information as part of immigration enforcement, according to a new cache of documents reviewed by 404 Media.

The documents peel back the curtain on a powerful system, both in a technological and a policy sense—how information is processed and used to decide who is allowed to remain in the country and who is not.