CRT stands for cathode ray tube, the display technology used in older televisions and monitors. A CRT is not a security control or a vulnerability by itself, but it is a strong signal that a system may be part of an older hardware stack. In cyber security, that matters because aging displays are often attached to legacy PCs, industrial consoles, point-of-sale terminals, or lab equipment that may run unsupported software or rely on outdated connections.
Attackers do not usually target the screen technology directly. Instead, a CRT can reveal an environment where patching is difficult, hardware replacement is delayed, or remote administration is minimal. Defenders see the same clue during asset discovery and incident response: a CRT-equipped workstation may deserve extra attention for compatibility risks, physical access concerns, and the likelihood of other obsolete components nearby. In short, CRTs are a reminder that old hardware can increase operational and security complexity.