Evasion is the deliberate concealment or modification of malicious code, commands, traffic, or behavior to bypass security controls and avoid detection. Common examples include code obfuscation, encrypted or rapidly changing payloads, abuse of trusted system tools, and disguising command-and-control traffic as ordinary network activity. It can target antivirus signatures, email and web filters, endpoint monitoring, or analysts investigating suspicious activity.
Successful evasion can reduce visibility, delay detection, and allow unauthorized activity to continue, although it may still leave behavioral or operational evidence. Mitigation should combine signature detection with behavior-based analytics and reliable endpoint, identity, and network telemetry. Restricting unnecessary scripting and administrative tools, applying application controls, and protecting centralized logs make abuse harder and preserve evidence. During investigations, examine process ancestry, unusual tool use, persistence changes, and deviations from expected user or host behavior rather than relying solely on file hashes or other easily changed indicators.