August 9, 2019
The US government’s maritime agency says it has received reports from ships in and near the Persian Gulf that someone is interfering with their navigation gear and sometimes radioing them with false claims to be US warships.
The US Department of Transportation’s Maritime Administration (MARAD) issued a warning August 7 to US commercial shipping.
It said that during “at least two” recent encounters involving Iranian military forces, “vessels reported GPS interference,” referring to the vessels’ use of Global Positioning Satellite (GPS) data to determine their own position at sea.
“Vessels have also reported spoofed bridge-to-bridge communications from unknown entities falsely claiming to be US or coalition warships,” the warning added.
The US Central Command, which oversees US military operations in the region, issued a statement the same day saying, “Vessels have reported GPS interference, bridge-to-bridge communications spoofing, and/or other communications jamming with little to no warning.”
A US defense official told CNN that Iran has placed GPS jammers on Abu Musa Island, which lies in the Persian Gulf close to the entrance to the Strait of Hormuz. The official said that had placed the jammers at that location in an attempt to disrupt civilian aircraft and ship navigation systems, hoping ships or planes would mistakenly wander into Iranian waters or airspace while their GPS systems were not functioning properly, giving Iranian forces the pretext to seize them.
The official said the Iranian jammers have no effect on US military warships and aircraft, meaning that the jamming did not impact the US military drone that was shot down last month. Iran claimed the drone was just inside Iranian territorial waters; the US said it was just outside.
The official told CNN Iranian boats have been “spoofing” the automatic identification system merchant ships use so as to disguise Iranian combat vessels as merchant ships.
The MARAD notice to US-flagged ships told them how they should act in response to Iranian contacts.
“If hailed by Iranian forces, US flag commercial vessels should provide vessel name, flag state, and affirm that they are proceeding in accordance with international law as reflected in the Law of the Sea Convention. The master should immediately inform the US Fifth Fleet Battle Watch.
“If Iranian forces seek to board a US flag commercial vessel navigating these waters, the ship’s master should, if the safety of the ship and crew would not be compromised, decline permission to board, noting that the vessel is proceeding in accordance with international law, and immediately inform the US Fifth Fleet Battle Watch.
“If Iranian forces board a US flagged commercial vessel, the vessel should immediately contact the US Fifth Fleet Battle Watch. The crew should not forcibly resist the boarding party. Refraining from forcible resistance does not imply consent or agreement to that boarding.”