A /24 network is an IPv4 subnet that contains 256 addresses, usually described by the mask 255.255.255.0. The first 24 bits identify the network, while the last 8 bits identify individual hosts. In practice, a /24 is a convenient chunk of address space to analyze because many related systems are assigned nearby addresses.
In cyber security, /24s matter because attackers often reuse hosting inside the same subnet or move across a small set of subnets to keep services online. Defenders use /24 grouping in threat hunting to cluster suspicious infrastructure, find shared control patterns, and pivot from one malicious IP to others that may be part of the same operation. It is useful for correlation, but it is not proof of intent by itself, so analysts combine it with DNS, TLS, routing, and traffic behavior.