The stranger who walks in behind you
Most people who get into an office without permission are simply let in. Here is how to be polite and still keep the door closed.
How tailgating works
A person carrying boxes, a courier in a hurry or someone who “forgot the badge upstairs” waits for an employee to open the door and follows them in. It works because holding a door is good manners and asking questions feels rude.
Once inside, the visitor can reach unlocked computers, network sockets, printers and papers. The door was the only control between them and all of it.
What to say
You do not need to confront anyone. “Hello, who are you here to see? I will walk you to reception” is friendly, and an honest visitor is glad of the help.
If someone without a badge is already inside, offer the same help. If they refuse or the answer does not make sense, tell reception or security and do not argue.
Rules that make it easy
Visitors are signed in, wear a visible badge and are accompanied by the person they came to see. Deliveries are received at reception. Rooms with servers, network equipment and archives stay locked, and the list of people with a key is short.
A lost badge or key is reported the same day so that it can be switched off. Nobody is blamed for losing one. The harm comes from a loss nobody mentioned.
This note is our own plain-language summary. For the full guidance, read the original: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/800-171r3/NIST.SP.800-171r3.html
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“Can I help you?” is the politest security control there is.