Tailgating gains entry to a physically restricted area by following an authorized person through a controlled door — exploiting politeness, authority cues, and the awkwardness of challenging a stranger, rather than presenting a valid credential. A badge reader or lock is a technical control, but the moment a real employee opens it, that control depends on a human deciding whether to admit the person behind them.
Several stagings recur: the hands-full ploy, where boxes or coffee trays make asking someone to badge in feel rude; a uniform or lanyard that borrows authority; joining a group at a propped smoke-break side door; or simply walking in with confident purpose so no one dares stop them. A near-sibling, piggybacking, is entry with the door-holder’s active but unwitting help.
Its defining feature: the barrier is technical, but the failure is social — a person choosing courtesy or conflict-avoidance over verification. Legitimate access invites verification; an intruder’s entry depends on the challenge not happening.