Sampling is the selection of a limited set of records, cases, devices, or sites to use as audit evidence. In cyber security, teams use sampling because it is often impossible to inspect every log entry, endpoint, account, or control. A good sample should be representative of the population being tested and aligned with the audit goal, whether that is checking access reviews, patching evidence, backup integrity, or incident response records.
Sampling matters because a small or biased sample can hide weaknesses and create false confidence. Defenders use it to validate controls efficiently, while auditors use it to test whether security processes work consistently across users, systems, and time periods. Attackers can also benefit when controls are only spot-checked, since gaps may remain unnoticed. The key risk is treating a passing sample as proof that the whole environment is secure; sampling supports evidence, but it does not guarantee completeness.