The U.S. naval blockade of Iranian ports, effective Monday, has spurred a surge in “shadow” tactics among vessels near the Strait of Hormuz. Windward’s chief executive, Ami Daniel, notes that ships now go dark or use random identifiers, echoing Russian shadow fleets that evade sanctions. The move complicates maritime surveillance for global trade.

Spoofing lets captains falsify origin, destination or transponder data, and even turn off the system entirely. Russian vessels have exploited this tactic to ship up to $100 billion in energy exports each year, keeping the war machine funded. Iranian-linked ships appear to be adopting the same playbook, according to Windward’s latest report for shippers worldwide.

By masking or falsifying identification, shadow vessels muddle the information environment that the U.S. Navy relies on to spot interdiction opportunities. With more than 12 American warships patrolling the Gulf of Oman, the blockade’s integrity hinges on accurate intelligence. A vessel that disappears on radar can still slip through, eroding the blockade’s deterrent effect today.

Six merchant ships have already turned back after U.S. radio orders, and U.S. Central Command confirms compliance. Daniel predicts the Navy can maintain a presence but admits breaches are unlikely. The new spoofing trend signals a tactical shift that could inflate costs for shipping firms and pressure insurers to adjust coverage premiums for.