This is posted on the IMO page: what are the concerns ans implications?
I have seen many people broadcasting the ships positions on the webb.

Maritime security - AIS ship data

At its79th session in December 2004, the Maritime Safety Committee
(MSC) agreed that, in relation to the issue of freely available
automatic information system (AIS)-generated ship data on the
world-wide web, the publication on the world-wide web or elsewhere of
AIS data transmitted by ships could be detrimental to the safety and
security of ships and port facilities and was undermining the efforts
of the Organization and its Member States to enhance the safety of
navigation and security in the international maritime transport sector.


The Committee condemned the regrettable publication on the world-wide
web, or elsewhere, of AIS data transmitted by ships and urged Member
Governments, subject to the provisions of their national laws, to
discourage those who make available AIS data to others for publication
on the world-wide web, or elsewhere from doing so.

In addition, the Committee condemned those who irresponsibly publish
AIS data transmitted by ships on the world-wide web, or elsewhere,
particularly if they offer services to the shipping and port
industries.