Sanctions Evasion Reference

Automatic Identification System

A mandatory maritime transponder system that broadcasts a vessel's identity, position, course and speed to nearby vessels and shore stations.

also known as

AIS

reviewed

2026-08-20

AIS was designed for collision avoidance, not for surveillance, and it is fundamentally a self-reported broadcast: the vessel transmits what its equipment is set to transmit. Ships are permitted to switch it off where the master judges that transmitting would compromise safety or security.

That legitimate exception is what makes gaps ambiguous, and it is why published guidance frames the indicator as a pattern rather than an event: transmission gaps that recur, that coincide with voyages to particular areas, or that cannot be reconciled with the vessel’s subsequent position.

Where this term is used

  • What is AIS manipulation and AIS spoofing? — Disabling a ship's position transponder, or transmitting false position data through it, so that the vessel's recorded track does not show where it actually went.
  • What is flag hopping? — Re-registering a ship repeatedly between flag states, often to registries with limited oversight, so that its regulatory history is broken and its documented identity keeps changing.
  • What is a ship-to-ship transfer? — Transferring cargo directly between two vessels at sea, rather than through a port, so that the cargo changes hands where there is no port authority, no customs entry and no independent record.

Related terms

  • IMO number — A seven-digit identifier assigned to a ship's hull for life by the International Maritime Organization, which does not change with name, owner or flag.
  • Ship-to-ship transfer — Transferring cargo directly between two vessels at sea or at anchorage rather than through a port terminal.
  • Shadow fleet — A loosely defined group of ageing tankers with opaque ownership and insurance that carry sanctioned or price-capped cargo outside mainstream shipping arrangements.

Sources

  1. Guidance to Address Illicit Shipping and Sanctions Evasion Practices. U.S. Department of State, U.S. Department of the Treasury and U.S. Coast Guard, 2020. Global maritime advisory, 14 May 2020.
  2. North Korea Vessel Advisory: Sanctions Risks Related to Shipping with North Korea. U.S. Department of the Treasury, Office of Foreign Assets Control, 2018.

All glossary terms