Spying can gather information or sabotage an enemy. Spy missions happen on a random planet or ship. Even the Steal Ship Plans mission will bring you a random ship plan if successful.

Launching a spy mission requires Spy Mana. This number represents operatives and information that is waiting to be used in your attack on the enemy. This amount will build up over time if you have highguard rangers. You can help gain more spy mana quicker by spending money from your central bank. If you attempt to spend far more than your spy operatives can use they will only spend what they need and leave the rest in the central bank.

Empires are more resistant to spying if they have high leadership, lawfulness and PSI rating. But the larger the empires the easier spy attacks. Empires with high light powers rating increases your spies chances of success, while a high dark powers rating increases how much damage the attack will do.

The Borg can not spy or be spied on.

To counter spy attacks you need high happiness, low crime, and at least one high guard. The more high guards you have the better chance of blocking, no effect with more than 20 high guards. There is always a 5% chance that a spy attack on a ship will still work no matter what.

40% of the time a high guard ranger can stop an enemy spy attack on a base that would have otherwise caused damage.