This post explains how the AIS vessel tracking system works and how bad actors abuse the system.

Miao Shou, Gaute Friis | AUGUST 21, 2023

Miao Shou

Analyst

Gaute Friis

Analyst

Tracking vessels’ Automatic Information System (AIS) signals is a core means SeaLight and other open-source intelligence collectors use to monitor maritime activity. AIS is a broadcast system that maritime authorities use to identify a vessel’s unique identification number, type, position, course, speed and navigation status. 

The International Maritime Organization (IMO) mandates the use of AIS to ensure maritime safety and direct marine traffic more efficiently. According to the International Maritime Organization’s International Convention for the Safety of Life at Sea (SOLAS) Regulation V/19.2.4, all vessels over 300 gross tons (or 500 tons for those not on international voyages) and passenger ships of any size are required to “carry automatic identification systems capable of providing information about the ship to other ships and to coastal authorities.” 

“Going dark” refers to the gray zone tactic of strategically turning off a vessel’s Automatic Information System (AIS) transponder to avoid detection.

Miao Shou | AUGUST 17, 2023

Miao Shou

Analyst

“Going dark” refers to the gray zone tactic of turning off a vessel’s Automatic Information System (AIS) transponder to avoid detection. AIS is a signaling system used to identify a vessel’s type, position, course, speed and other navigation safety information, and is required by the International Maritime Organization for larger non-military ships operating in international waters. Read our primer on the AIS system here.
 
Going Dark in the Recent Water Cannon Incident

In a recent incident that involved the blockade and water-cannoning of a small Philippine resupply vessel and its escorts, six of the blockading ships were from the China Coast Guard. Of these, only one ship (CCG 5402) remained AIS-visible during the entire engagement, while two other ships (CCG 4203 and CCG 3302) broadcast AIS only intermittently.