This Elite Security guard has armor level 1.

The corps are now issuing high-tension personal armor to their security forces as standard equipment. I think they're getting scared of us. It would be flattering if it didn't represent an existential threat. Make sure you bring along something extra pointy for emergencies.
—Central

Many guards have armor, which prevents some attacks against them. An agent can only attack an armored guard if the armor piercing of the agent's weapon, plus any armor piercing bonuses, is at least equal to the guard's armor level. If the agent does not have sufficient armor piercing then they are unable to target the guard with the attack. A guard's armor level is shown in a shield icon above them.

Armor protects guards against attacks using weapons, including attacks made during the enemy turn while on ambush or overwatch, and including attacks made by agency-controlled drones or Turrets. Armor does not protect against items such as Flash Grenades or Shock Traps, regardless of the guard's armor level. Armor also does not protect guards against agency-controlled lethal Laser Panels.

Each type of guard has a base armor level, which can be raised by the daemon Chiton, and reduced by the Aces program. Barrier Guards and OMNI Protectors have a variable base armor level, depending on their number of firewalls.