What is tailgating and how is it prevented?

Tailgating, also called piggybacking, occurs when an unauthorized person follows an authorized person through a secured door or entry point without presenting their own credentials. It exploits social courtesy where people hold doors open for others. Prevention measures include mantraps or security vestibules that allow only one person through at a time, turnstiles, anti-passback systems that prevent a credential from being used twice to enter without an intervening exit, security awareness training teaching employees not to hold doors and to challenge unknown individuals, and security gu