(COMSEC) [The] interception, alteration, and retransmission of a cipher signal or data in such a way as to mislead the recipient. [NIS] 2. (AIS) [An] attempt to gain access to an AIS by posing as an authorized user. [NIS] 3. Unauthorized use of legitimate Identification and Authentication (I&A) data, however it was obtained, to mimic a subject different from the attacker. Impersonating, masquerading, piggybacking, and mimicking are forms of spoofing. [INFOSEC-99]