Actually, the game should make it difficult to find out whether the "AI" is really an AI or a human.

Hmm, one way of doing that would be having certain types of attacks being "viruses", that wreak havoc in an enemy's computer systems; so it's normal from everybody's point of view if they act "random" - though some may actually be AIs.

Another way of making hidden AIs more interesting would be having "covert actions" a regular mechanism of the game - sabotage of systems, espionage, alerts that "something" is going on, stealing technology ... so if you have signs of covert actions going on, you don't know if it's a rogue AI or one of your enemies.