Oops: Inexpensive personal trackers have made finding items a trivial matter, but they come with some security risks. Recently, a €5 consumer gadget was enough to briefly track the movements of a modern European warship, showing how easily these low-cost devices can slip into operational blind spots.
Dutch regional broadcaster Omroep Gelderland reported that one of its journalists tracked HNLMS Evertsen, a Dutch air-defense frigate, during an active deployment in the eastern Mediterranean. The ship was operating to help protect France's aircraft carrier Charles de Gaulle against missile threats when the tracking occurred.
The breach required no specialized equipment. Journalist Just Vervaart concealed a Bluetooth tracker inside a postcard. He then mailed it to the vessel using publicly available instructions from the Dutch Ministry of Defense, intended to help families send mail to loved ones stationed on the ship. This protocol provided enough details to get the tracker aboard the ship.
Once delivered, the tracker transmitted location data for roughly 24 hours. During that window, it showed the Evertsen departing from Heraklion, Crete, traveling west along the island's coastline, and then turning east toward Cyprus. The signal stopped the following day when the ship was near Cyprus and has not resumed since.
Defense officials later confirmed to the broadcaster that staff discovered the device during internal mail sorting and disabled it. Even so, the incident has already led to procedural changes. The Ministry is now moving to ban greeting cards containing batteries and is reviewing broader mail-handling guidelines.
The Register noted that Ministry guidance and informational videos indicated that envelopes were not subject to X-ray screening, unlike parcels. That gap allowed the tracking device to slip through ordinary mail.
Bluetooth trackers rely on nearby smartphones and other connected devices to relay location data. Originally designed to help locate lost personal items, they depend on distributed networks of nearby devices to function. In everyday use, that infrastructure is mostly harmless. In a military setting, it creates a quiet way to leak location data, especially when paired with predictable logistics.
Retired Dutch Lieutenant General Mart de Kruif framed the issue in terms of targeting precision enabled by modern technology.
"Nowadays, you can eliminate targets remotely and with great precision, but you do need to know where they are," he told Omroep Gelderland. "So, as a frigate, you never want to reveal your location to other people."
Balancing accessibility and security is not new, but the technology involved has changed. Practices once seen as low risk – like publishing mailing instructions or allowing unscanned letters – now intersect with cheap, widely available tracking hardware.
From a military standpoint, the incident shows that operational security can be weakened not by advanced tools, but by the combination of open information and cheap consumer technology. The same dynamic applies to enterprises, where convenience-driven processes can create exposure when paired with modern sensing and networked devices.
In this case, a controlled journalistic test exposed the vulnerability. The broader concern is that similar techniques require little expertise, minimal cost, and no privileged access – only an understanding of how everyday systems can serve new, potentially malicious, purposes.
A $5 Bluetooth tracker hidden in a postcard exposed a warship's movements
