STRAIT OF HORMUZ — Windward AI tracked 148 "dark activity" events in the Strait of Hormuz on Wednesday, periods when ships turned off their transponders to evade detection, according to the maritime intelligence firm. Michelle Wiese Bockmann, a senior maritime intelligence analyst at Windward AI, reported that well over half of the vessels in the strait had their signals jammed.

Transponders typically broadcast ships' names, locations, routes, and IMO numbers. Shadow fleets that violate international sanctions by transporting crude oil from Iran have periodically turned off their transponders for nearly a decade. Two-thirds of tanker traffic moving through the Strait of Hormuz is by vessels with histories of violating sanctions.

"Those vessels use every single deceptive shipping practice in the book," Bockmann said. More than 800 vessels are currently in the Persian Gulf, according to Windward AI data, and Bockmann monitors a cohort of 500 to 600 tankers, some of which she has watched for years.

Approximately 20 percent of the petroleum consumed globally moves through the Strait of Hormuz. Tankers that do not broadcast their locations can collide with other vessels or run aground, increasing the risk of catastrophic oil spills. Disruption there, Bockmann said in a podcast interview, creates "absolute carnage and chaos."

Windward AI works with marine insurers, oil traders, and other financial institutions that have interests in or onboard hundreds of ships that typically move through the strait every month. Analysts combine satellite imagery, radio-frequency data, ship registry databases, and human presence signals from onboard mobile devices to track vessel movements. Electro-optical imagery uses electronic sensors to detect visible and near-infrared light, while synthetic-aperture radar uses microwaves to create images even through clouds, rain, or darkness. Radio-frequency signals are used to transmit data wirelessly. Satellite imagery was once very expensive to obtain, but its prices are decreasing.

Bockmann, who has been tracking shipping across the globe for 30 years, may recognize a ship visually based on years of tracking it and can reverse engineer a ship's route to another port of call to determine its location. Last month, she used historical data and simple geometry to confirm that sanctioned oil tankers were using a new route to travel to ports with Iranian permission. Israel and the United States attacked Iran in late February. "When it comes to Iran, having 100 percent visibility is not possible," she said.