All Security System types can defend against Missiles.
If a Missile’s power exceeds the combined power of Security Systems active at the Base, then all of the Security System Units will be lost. The remaining power of the Missile will be inflicted on your other Units.
If the Missile’s power is less than the combined power of the Security System Units, the Missile will inflict some damage to the Security Systems (some will be lost), and the Missile Attack is considered a failure.
Remember to upgrade your Security Systems by researching Tech to get the best results. Share this knowledge with your Alliance to better defend against your enemies.