The Department of Homeland Security's border patrol drones are outfitted to distinguish armed subjects from unarmed ones and to potentially intercept communications signals. Earlier this week, the Electronic Privacy Information Center received a redacted document from the Bureau of Customs and Border Protection through the Freedom of Information Act, showing the performance specifications of Predator drones that are used to patrol the US border. Later, CNET found an unredacted copy. Among other things, the specifications include a surveillance system that is "capable of identifying a standing human being at night as likely armed or not (based on position of arms)."
Besides the visual surveillance system, border patrol drones also incorporate interception of wireless signals. Though use cases aren't specified, the drone should be able to detect multiple signals and communication links for direction-finding, and also to include a "signals intercept airborne suite" that can pick up a range of spectrum. While detecting weapons makes sense in light of how law enforcement sees drones as a way to watch for potential criminals without putting its own people on the line, signal interception opens up new and unsettling surveillance opportunities, especially as drones become more common.
"Any potential deployment... would be implemented in full consideration of civil rights."
Right now, the Department of Homeland Security tells CNET it's not deploying the interception capabilities, and that "Any potential deployment of such technology in the future would be implemented in full consideration of civil rights, civil liberties, and privacy interests and in a manner consistent with the law and long standing law enforcement practices." An unnamed official suggests that it was added as a form of future-proofing, because of the surveillance drones' long lifespans. If Homeland Security does start using it, however, there's a good chance we won't find out for a long time.