Displaying conspicuous warning signs that clearly state 'No Trespassing - Violators Will Be Prosecuted' around the perimeter of a data center is considered an example of a deterrent control.
Deterrent controls are designed to discourage unauthorized individuals from attempting to breach the physical or logical perimeter of a secure environment. Warning signs are a physical representation of such measures and aim to dissuade potential trespassers by informing them of the legal repercussions. This method does not prevent an attack itself but influences behavior by the threat of legal action or other negative consequences.