The armour glitch, or 10,000 point flak jacket glitch, is a Syphon Filter: Omega Strain technique in which a player can potentially equip body protection with said amount of points.
This can only be performed during North Atlantic: Lorelei Salvage Rig. From the topside deck, neutralise or evade the first two security guards and then use the jump glitch to access the platform near Mujari. Climb the stairs to find him and hit him with a non-lethal weapon. He will surrender a 10,000 point flak jacket. (And no, I am NOT bullshitting you!)
A video on it can be found here.