In cyber security, common practice means a shared way of interpreting evidence, controls, or risk so that different teams reach similar conclusions in similar cases. It does not replace policy or law; instead, it gives analysts, auditors, and defenders a consistent baseline for judgment. When a security issue is reviewed across systems, a common practice helps answer questions such as whether a control is normal, whether a configuration is acceptable, or whether an event should be treated as suspicious.
This matters because attackers often exploit gaps between what one team considers acceptable and what another team misses. For example, weak authentication settings, inconsistent logging, or unusual access patterns may stand out only when compared with common practice. Defenders use the same idea to standardize incident triage, vulnerability review, and compliance checks. In practice, common practice helps reduce ambiguity, improve repeatability, and make security decisions easier to defend across cases.