The security ministry also helps to defend your planet from foreign spies by intercepting the ships carrying them. The higher the level the better the chance to intercept. The formula for determining whether or not the security ministry will intercept incoming ships filled with spies is:
Ships intercepted are destroyed.
In addition, the security ministry will show you any foreign spies that are on your planet that have a level equal to or below the level of the ministry. It also allows you to manage your prisoners; you can view, release, or execute them.
Because of its oppresive nature the security ministry drains happiness from your planet.
Also, executing prisoners costs happiness.