or performs a malicious act by posing as an authorized entity. "Spoof" Attempt by an unauthorized entity to gain access to a system by posing as an authorized user. "Malicious logic" In context of masquerade, any hardware, firmware, or software (e.g., Trojan horse) that appears to perform a useful or desirable function, but actually gains unauthorized access to system resources or tricks a user into executing other malicious logic. "Falsification" A threat action whereby false data deceives an authorized entity. (See: active wiretapping.) "Substitution" Altering or replacing valid data with false data that serves to deceive an authorized entity. "Insertion" Introducing false data that serves to deceive an authorized entity. "Repudiation" A threat action whereby an entity deceives another by falsely denying responsibility for an act. "False denial of origin" Action whereby the originator of data denies responsibility for its generation. "False denial of receipt" Action whereby the recipient of data denies receiving and possessing the data. "Disruption" (a threat consequence) A circumstance or event that interrupts or prevents the correct operation of system services and functions. (See: denial of service.) The following threat actions can cause disruption: "Incapacitation" A threat action that prevents or interrupts system operation by disabling a system component. "Malicious logic" In the context of incapacitation, any hardware, firmware, or software (e.g., logic bomb) intentionally introduced into a system to destroy system functions or resources. "Physical destruction" Deliberate destruction of a system component to interrupt or prevent system operation. * "Human error" Action or inaction that unintentionally disables a system component. * "Hardware or software error" Error that causes failure of a system component and leads to disruption of system operation. * "Natural disaster" Any natural disaster (e.g., fire, flood, earthquake, lightning, or wind) that disables a system component. "Corruption" A threat action that undesirably alters system operation by adversely modifying system functions or data. "Tamper" In the context of corruption, deliberate alteration of a system's logic, data, or control information to interrupt or prevent correct operation of system functions. "Malicious logic" In the context of corruption, any hardware, firmware, or software (e.g., a computer virus) intentionally introduced into a system to modify system functions or data. * "Human error" Human action or inaction that unintentionally results in the alteration of system functions or data. * "Hardware or software error" Error that results in the alteration of system functions or data. * "Natural disaster" Any natural