A commercial ship docks at Al-Salif port on May 12, 2024, in the Red Sea, Yemen.

A commercial ship docks at Al-Salif port on May 12, 2024, in the Red Sea, Yemen. Getty Images / Mohammed Hamoud

The double-edged global ship tracking system

Houthi groups have used public tracking data to target commercial ships—revealing that staying undetected is trickier than just going dark digitally.

The tracking systems merchant vessels rely on to navigate their routes are the same ones Houthi groups use to target them. But turning off the systems isn't a simple solution. 

“The vast bulk of the global economy relies on shipping to get its activities moving. And what we've seen currently happening in the Red Sea with the Houthi attacks against international shipping there is that the system that was designed to make that shipping more efficient, more safe, and just get us all of the stuff that we want to have happen, has got an inherent bug in it,” said Col. Sean Heidgerken, advisor and head of public affairs for U.S. Central Command, during an Association of the U.S. Army event Tuesday. 

The Automatic Identification System is a global tracking system that functions as a ship's beacon so companies can follow vessels on their routes, and ports can keep track of and prepare for incoming shipments. 

“It tells everybody exactly where you are with GPS. The Houthis are using that because it's publicly available, you can get a subscription, you can see it,” he said. 

But while some companies have tried turning off the system to avoid detection, that doesn’t always work. 

“Shipping is all about efficiency. So ship captains, even if they turn off their AIS when they enter into a dangerous area, you can pretty much assume that their behavior is not going to change. They're going to continue to drive in a straight line at a set course and speed, because that's what's efficient. And it's all about making the money,” Heidgerken said. 

Ships have been advised to turn off AIS, Heidgerken said, but it’s not clear where to flip the switch in order to throw off Houthi trackers. Additionally, Houthi radar sites along the coastline plus off-the-shelf tracking and navigation technology can help map out ships’ locations without the AIS signal.

The U.S. launched military strikes on Houthi radar sites in Yemen after a merchant sailor went missing in June. Since November, Iran-backed Houthi groups have attacked around 50 international shipping vessels, seized one, sank two, and killed three people.

The world of commercial shipping is also complicated because a vessel can be owned by a company from one country, fly a flag from another country, and staff it with workers from various other countries, Heidgerken said. 

Modern warfare increasingly involves detecting, masking, jamming, and spoofing the digital signals emitted from high-tech weapons and communications devices. But in the Red Sea, where military and commercial activity intertwine, matters are further complicated by the ubiquitous use of the AIS system, which can’t be unilaterally turned off or blocked by the U.S. government to prevent ships from being targeted. 

“I'm not sure how many people fully understand the murky world that is international shipping as to who owns, flags, mans, equips…on a ship,” he said. “But the ships that have been struck have tended to have their AIS on.”

And there are other sensors collecting data as well, so ships have to adapt and experiment with different ways to slip under the radar. 

“There's a lot of different things being tried there, whether it's taking out the sensors, whether it's advising ships to travel in a certain way. You've actually seen reports where…a ship will be hit, the ship's captain will report that they weren't hit, just so that it doesn't give the data back to the Houthis to then restrike because they think that there might be an opportunity there. Plus, there's also the financial side of it: that raises insurance rates, which raises the cost of shipping, and all these things are intertwined in a way that is not typically understood or thought about, I think, in the military environment. So perhaps the real answer is, this is not a problem that the military can necessarily solve on its own,” Heidgerken said. 

And with the increased use of artificial intelligence tools, there’s no guaranteed advantage in flooding an adversary with data. 

“I think we used to look at data and information in a way that we could, perhaps, overwhelm the adversaries' decision-making process by giving them so much data that it put them into some form of a vapor lock. With the current technologies that are just resident off-the-shelf, using some simple AI tools that are out there, it helps cull through that data in a way that I'm not sure right now we can overwhelm,” he said. “When you balance that with the problem of no data, that black hole tells you something, too: now you can analyze that. We haven't quite figured it out. But it's a great testbed,” he said.