Russia’s “Shadow Fleet” Systematically Forges IMO Numbers of Maritime Vessels: How to Screen Suppliers for Sanctions Compliance

“Zombie tankers” is the term used in the maritime industry to describe vessels that change their “identity” in order to continue transporting oil and petroleum products in circumvention of international sanctions.

This phenomenon has become a new challenge for sanctions compliance and international maritime auditing. The defining feature of such vessels is the falsification of unique IMO identifiers, which renders traditional supply chain analysis ineffective.

TriTrace Investigations examines how the international vessel identification system operates, how “shadow fleet” operators circumvent it, and how to mitigate sanctions risks associated with such vessels.

What is an IMO number: a unique vessel identifier

An IMO number is a unique identifier assigned to a maritime vessel, consisting of seven digits. It can be compared to a vehicle registration number that remains with the vessel throughout its entire operational life. It is retained even if the vessel changes its name or flag.

The system was established by the International Maritime Organization (IMO). Work on a unified identification standard began in 1987. Since 1996, IMO registration has been mandatory for passenger vessels of 100 gross tonnage and above, as well as for all cargo vessels of 300 gross tonnage and above.

The IMO number itself does not encode any specific information about the vessel. It serves solely as a unique identifier and cannot be decoded. However, using the IMO number in conjunction with international registries, it is possible to obtain information on the vessel’s country of registration, technical characteristics, owners and operators, as well as related legal entities.

How the “Shadow Fleet” Falsifies IMO Numbers

The global sanctions evasion industry consistently requires “clean” vessels — ships that are not listed under sanctions imposed by the United States, the European Union, or other jurisdictions. One of the most common methods is the large-scale acquisition of aging tankers on the secondary market.

However, in 2025, a new scheme emerged: the falsification of IMO numbers. According to the industry publication Lloyd’s List, this practice has taken on a “systemic” nature.

One example is the Iranian “shadow fleet” tanker Macho Queen (IMO: 9238868). This vessel was sanctioned by the United States on August 21, 2025, and within a month — on September 26 — the tanker resumed operations under the new name Lavin. To conceal the vessel’s origin, its operators used the IMO number of the tanker Pedrot (IMO: 9177686), which had been scrapped in 2018.

How to identify a “zombie tanker”

Chartering, insuring, servicing, or engaging in any other form of cooperation with such vessels may result in criminal investigations, multi-million-dollar fines, and even secondary sanctions. Regulators, however, rarely take into account how difficult it can be to detect the falsification of a vessel’s identity.

Nevertheless, several methods exist for identifying so-called “zombie tankers.” The primary tool is the Automatic Identification System (AIS). This is a global transponder-based system through which vessels transmit their coordinates, course, speed, and identification data. AIS enables the reconstruction of a vessel’s route. Through OSINT analysis of this data, it is possible to determine the true IMO number of a “zombie tanker.”

Another reliable method is the comparison of satellite imagery. Even if a vessel has changed its name, flag, and IMO number, its physical characteristics might remain unchanged. By comparing hull dimensions— such as length and beam — and other visual indicators, investigators can determine whether a vessel is part of the so-called “shadow fleet.”

Entrust your supply chain due diligence to professionals with over 15 years of OSINT investigative experience. TriTrace Investigations conducts background checks on exporters and suppliers for potential links to Russia. Further details on this and other services are available in the relevant section of our website.