Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Phase: Operation
Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
Phase: System Configuration