Following a thread on uk.rec.boats about pirates ......

All vessels over 200 tonne are supposed to carry AIS transmitters. Does
anyone know what the regulations are if you *want* to carry AIS being
under 200 tonnes? How does anyone police the use of the system. It
appears to me that there is no registration id of the transmitting
equipment and anyway that could be falsified.

Has anyone considered what would happen if someone was to start
transmitting false 'echoes'. The original idea was to masquerade as a
naval ship if threatened by pirates. It might at least make them think
twice if they thought there was a chance that someone with bigger guns
than them was nearby.

Ian