Iranian agents are offering deep discounts to buyers willing to create false documents and move the Iranian crude. This is risky, for those who get caught can be prosecuted, jailed, and fined. But Iranian smugglers know who is willing to take chances, if the payoff is large enough. Selling oil at discounts of 30 percent or more still costs Iran. So also does the expense of secretly buying tankers that will pretend to belong to another country while moving the black market oil. This is where the false GPS locations are put out by the transponders.
The U.S. and the UN are alert to these schemes and the great game of cat and mouse is on. While Iran has been successful in the past, that was because it was often moving items (like weapons components) that could be hidden in a cargo container. Oil is another matter. Iran has experimented with using shipping containers to smuggle oil but this is very inefficient and you can still get caught. Iran fears that between the CIA (photo satellites and spies) and the maritime insurance industry (that monitors world shipping via transponders and other sightings) it will be very difficult to move the illegal oil. How difficult will probably be better known as time goes by.
This led Iran to come up with ways to confuse the international ship tracking system. These “maritime security technologies” were developed as a safety feature and have proved valuable, providing the positions of ships caught in storms or taken by pirates. AIS (Automated Identification System) and INMARSAT (International Maritime Satellite) were originally developed to make it easier for ships to track other nearby ships at sea. AIS is essentially an automatic radio beacon (transponder) that, when it receives a signal from a nearby AIS equipped ship, responds with the ship's identity, course, and speed. This is meant to enable AIS ships to avoid collisions with each other. INMARSAT is a more elaborate and longer range system. It enables shipping companies the ability to keep track of their vessels, no matter where they are on the planet. INMARSAT uses a system of satellites, which transmit AIS-like signals to anywhere on the oceans. It only costs a few cents to send an INMARSAT signal to one of your ships and a few cents more to receive a reply. All ships now use GPS coordinates to record location. Iran often just has two ships trade INMARSAT IDs while they are near each other, leaving the U.S., or anyone else checking INMARSAT data, unable to track ships that have been switched.
These two systems are now required by law (international agreements) for all sea going vessels greater than 300-tons. The technology has worked, and the U.S. Navy has found them particularly useful in counter-terror operations. Coast Guards the world over have also found the systems a big help. But apparently pirates in some areas have gained access to the systems (via bribes or theft) and an increasing number of pirate attacks appear to have been helped by technology meant just to safeguard ships at sea. Iran, and other nations involved in smuggling, learned how to have INMARSAT send a false signal, concealing where the ship actually is. This can work for a while but a nation with lots of recon satellites, warships, and cooperation from most of the world’s shipping can get around this.
The Iranians are aware of the satellites and other means of double-checking transponder data and is constantly coming up with schemes to confound the American snoopers. Since Iran has been under sanctions for decades for being an outlaw state, threatening more punishment is seen as a challenge not a threat.