The verification stack
Photo ID → visitor booked in → host contacted and confirms → pass issued with time limit → escort where policy requires. Skip any step and the record becomes deniable.
Tailgating countermeasures
Airlocks, mantraps, sensor-based alerts, and the human intervention — every guard trained to politely intercept and check anyone following through on someone else's fob.
The 'social engineer'
The urgent-looking delivery driver, the executive who 'left their pass at home', the contractor whose boss is 'expecting them'. All are classic social-engineering patterns. Verify, don't accommodate.