R.B., KN.A.N.O Security Gaurd is an enemy in Red Faction II. They are the first enemies you encounter and are only encountered in the first mission, set two years before the true events.
R.B.'s wear a gray and maroon uniform, with a maroon beret. They are directly encountered as soon as you enter the courtyard. The ones on the ground(and the catwalks) are armed with Assault Rifles, while the ones in the four towers are armed with Sniper Rifles. In the motorpool, there is an infinite amount of R.B.'s that come into the control room overlooking it, mainly two at a time. In the main corridor, they fight alongside Slammer Sammies, and many are armed with Pistols and Machine Pistols.
R.B.'s are basically the "pre-version" of Military and Urban Military units of Sopot. Since you have a Prototype N.I.C.W., they shouldn't be a hassle. They can be dangerous if fought in a group, since your health doesn't regenerate unlike in all other parts.