špijunirati

1. to spy
   Godinama je špijunirao za stranu službu. — He spied for a foreign intelligence service for years.
2. (+ acc.) to spy on
   Komšinica nas stalno špijunira kroz prozor. — Our neighbor keeps spying on us through the window.
   Aplikacije nas špijuniraju i skupljaju podatke. — Apps spy on us and collect data.

The person spied on is a direct accusative object (špijunirati koga); the side one spies for takes za + accusative.