AIS spoofing manipulates identifying or voyage information to mislead operational pictures.
UK OFSI guidance defines AIS spoofing as manipulation of AIS data that allows a ship to broadcast different identifying information and can conceal its next port of call or other voyage information; the same guidance describes manipulation used to mask movement. Missing or incorrect AIS information has multiple explanations. Legitimate disablement for safety, poor transmission, sensor or configuration faults, stale manual input and deliberate manipulation are distinct from the specific act of spoofing itself.
A VTS may broadcast a clearly identified synthetic AIS target for a vessel that does not carry AIS and is tracked by VTS radar; third-party-relayed target data may be less complete than directly received ship data. A virtual AIS aid to navigation is an official navigation mark presented at a reported position; it is not a broadcast claiming that a physical ship exists there.
AIS is supplementary information and discrepancies should be assessed against radar, visual observations and other available safety information rather than treated as proof of spoofing, purpose or actor. USCG guidance describes AIS as an open, unencrypted system in which false or ghost targets are technically possible, and advises corroboration and reporting rather than reliance on the AIS display alone.
