A mutation is a change in a genetic sequence that can alter how a gene or organism functions. In biology, it may be harmless, helpful, or harmful depending on where it occurs and what it changes. The key idea is that small changes can have large effects on the behavior of a complex system.
In cybersecurity, the same word is used for code or data that is deliberately changed to evade detection or to trigger different behavior. Malware may mutate its file structure, strings, or control flow so signature-based tools see a new sample each time. Defenders respond by looking for behavior, similarity, and patterns that survive surface changes. Mutation also appears in testing: fuzzers mutate inputs to uncover crashes, logic bugs, and parser weaknesses by making many small variations to a target program.