Bluetooth tracker hidden in a postcard and mailed to a warship exposed its location — $5 gadget put a $585 million Dutch ship at risk for 24 hours

A Dutch journalist mailed a postcard with a hidden Bluetooth tracker to HNLMS Evertsen after following public mail instructions, and the device revealed the frigate’s position for about a day.

The tracker was eventually found and disabled, but the incident showed how inexpensive consumer gadgets can expose military movements.

In response, the Dutch Ministry of Defense tightened mail security rules for the ship.

The breach highlights how open-source information and simple tracking devices can threaten naval operations without direct access to the vessel.