By SanctionsAI team · Updated 2026-08-09

Ship-to-ship transfers and flag hopping evasion

Maritime sanctions evasion involves ship-to-ship (STS) transfers at sea, AIS signal manipulation, and flag hopping to disguise the origin of sanctioned commodities like Iranian and North Korean oil.

TL;DR: OFAC has issued multiple advisories on maritime sanctions evasion. Sanctioned entities use STS transfers to blend sanctioned oil with legitimate cargo, disable AIS (Automatic Identification System) to hide ship locations, and repeatedly change vessel flags to evade tracking.

OFAC maritime sanctions advisories

OFAC, in coordination with the State Department and Coast Guard, has published detailed advisories on illicit maritime activity including: the Iran shipping advisory (2020), the North Korea shipping advisory (2018, updated), and the Global Maritime Sanctions Advisory (2021). These advise the shipping, insurance, and financial sectors on detecting sanctions evasion.

The three main maritime evasion methods

MethodHow it worksOFAC advisory response
STS transfers at seaSanctioned cargo transferred between ships in international waters to disguise originScreen STS locations and dates; flag transfers in high-risk areas
AIS disablingShips turn off tracking before entering sanctioned ports or conducting illicit transfersTreat AIS gaps as red flags; require continuous tracking
Flag hoppingVessels repeatedly change flag state to evade tracking or sanctions enforcementScreen vessel IMO numbers, not just flag state

Relevance to AI agent payments

Maritime sanctions evasion is relevant to compliance teams in shipping, trade finance, and insurance. For AI agents handling digital payments, this is a lower-priority vector, but agents processing trade finance documentation or shipping payments should be aware of STS transfer red flags.

Key red flag: AI agents processing shipping payments should flag transactions involving vessels with AIS gaps, STS transfers in high-risk areas (South China Sea, Persian Gulf), or vessels that have recently changed flag state.

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Frequently Asked Questions

What is AIS disabling?
Ships turn off their Automatic Identification System (AIS) transponder to hide their location. OFAC advisories treat AIS gaps as sanctions evasion red flags, especially near comprehensively sanctioned jurisdictions.
What is ship-to-ship transfer evasion?
Transferring sanctioned cargo (typically oil) between ships at sea to disguise its origin. The receiving ship blends the sanctioned cargo with legitimate cargo, making it appear to have originated from a non-sanctioned source.
Has OFAC designated ships for sanctions evasion?
Yes. OFAC has designated numerous vessels under the Iran and North Korea sanctions programs for involvement in maritime sanctions evasion. Designated vessels are blocked property; US persons cannot charter, insure, or transact with them.
What is flag hopping?
Vessels repeatedly changing their flag state (country of registration) to evade tracking or sanctions enforcement. OFAC advises screening vessels by IMO number rather than flag state to detect this.

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