Security Magic is the Talent associated with protecting things and people. Security Mages are called Warders. Several different types of wards and shields can be used.
The aura color typically associated with Security Magic is cyan.
Shields are physical protection, and this branch of magic is often considered to be related to telekinesis. A shield around a person can stop or deflect incoming attacks or projectiles. A more specialized shield can stop certain things from coming through while permitting access to other things. This, of course, requires much more skill than simply blocking everything.
Wards are magical protection. They do nothing to stop physical objects from passing through, but protect against certain types of magic. For instance, a ward can be set up to prevent Scrying or teleportation into an area. Simple wards against Mind Magic can be used even by those with otherwise no training in it, but they will rarely stop a strong or skilled enough telepath.