We have had two canon security robots in BattleTech products.
The first, from MechWarrior 1E, was a Star League era design intended to provide perimeter security at SLDF bases and interior security in Castles Brian. They are six-ton hovercraft with one ton of armor and two small lasers in a turret, capable of 12/18 movement with a Class 30 fusion engine, and autonomous with .3 tons allocated for robotic controls.
The second, from a Kell Hounds scenario, is a far larger, but more primitive security robot - moving about 1 hex every ten turns, it mounts at least 10 tons of armor, has treads instead of legs, and packs two arm-mounted machine guns. It was deployed by House Marik to supplement the garrison in a bunker for storing nuclear warheads, and performs best in tight quarters. It is intended to be guided by an operator, but proved prone to systems malfunctions, resulting in it attacking anything that moves, rather than relying on IFF systems.