Passive Attack definition in Computer Security terms:
Definition(s): An attack that does not alter systems or data.
Source(s): CNSSI 4009-2015
An attack against an authentication protocol where the Attacker intercepts data traveling along the network between the Claimant and Verifier, but does not alter the data (i.e., eavesdropping).
Source(s): NIST SP 800-63-2
reference: CSRC Glossary