Friction is the resistance that acts when two surfaces touch and move against each other. In simple vibration-driven machines, that resistance is what turns rapid shaking into small steps of forward motion. Without enough friction, a brush bot would slip; with the right amount, its vibration can be converted into controlled movement.
In cyber security, friction matters anywhere physical motion or contact is part of the system: locks, badge readers, printers, robots, and tamper-detection hardware. Attackers may exploit poor friction by jamming a mechanism, forcing a sensor out of tolerance, or making a device misread its state. Defenders account for friction with material choice, surface texture, spring tension, and wear testing so mechanisms stay predictable, harder to bypass, and easier to monitor for interference.