That’s not all

The American imperialists are constantly on the tail of the North Koreans, spying on them from every angle conceivable. 
They send these smart self-guided torpedo things (they have a militaristic name that involves notions of ballistic espionage unfamiliar to me) into North Korean waters and then they call them back and analyze the data.

This one, obviously, was caught and never made it back. It was intercepted in 2004.