The death of thousands of security and military personnel in the Battle of the Citadel was a loss felt throughout the galaxy. As large numbers of qualified personnel transferred to the Citadel to replace those that died, short-handed security companies filled out their numbers with large-scale use of unmanned security robots. Commonly referred to as "mechs", the security robots are typically grouped into light and heavy varieties. Light mechs come in a variety of sizes but are easily distinguished by opposable digits that help them in their versatile security roles. Heavy mechs lack digits and are simply weapons platforms intended to keep the peace in high-threat areas. The quadrupedal dog mech has a "face" composed of contraband-detection sensors, and it too is armed in case a perpetrator resists arrest.
A typical security mech has an extremely limited virtual intelligence. Its duty is straightforward and narrow, usually to guard an area, run a friend-or-foe program to halt unauthorized access, and fire a set of prerecorded voice commands to warn troublemakers away from the area. Light security mechs are equipped with irritant sprays and electroshockers to force compliance, and heavy mechs may be outfitted with flash-bang stunners for similar purposes. When facing an opponent armed with a firearm, any mech will immediately resort to lethal antipersonnel weapons to neutralize the threat. If the situation turns violent rapidly enough, it may not even use its warnings.
Security mechs are frowned upon for actual military duty. Though tough enough to survive most firefights, their VI simply does not have the programming to plan an ambush, rescue a hostage, treat a wound, or any of countless other objectives that a soldier must be able to perform on the fly.