Most guards are classified roughly according to their relative danger to the player. The game difficulty setting and mission difficulty level determine how many guards of each class will be present at the start of a mission.

Some enemy units are not classified because they appear depending on the type mission, regardless of the mission difficulty setting:

• Captains appear in Detention Centers, some Security Dispatches and some Vaults.
• Financial Executives appear in Chief Financial Suites.
• Refit Drones appear in Drone Rescue side-missions.
• Scientists appear in Program Compile side-missions, and in the OMNI Foundry Lab mission.

Additionally, Enforcers and Elite Enforcers are not classified, because they are never present at the start of the mission.