Just Vervaart and Omroep Gelderland
Dutch journalist Just Vervaart, working for regional media network Omroep Gelderland, followed directions posted on a Dutch government website to conceal a tracker inside a mailed postcard. Vervaart’s experiment produced the only named, verifiable demonstration in the published account: a journalist using publicly available instructions to place a tracking device in mailed correspondence sent to a naval vessel.
The hidden Bluetooth tracker technique
The device in question was a Bluetooth tracker concealed within an electronic greeting card mailed as a postcard. The tracking succeeded long enough to provide location data: Vervaart and the outlet were able to follow the ship’s movement for roughly a day. The account ties the method explicitly to publicly posted instructions on a Dutch government site and to the simple medium of mailed correspondence rather than a larger parcel.
Voyage observed: Heraklion to Cyprus
The tracking output documented the vessel’s movement from Heraklion, on the island of Crete, until it turned toward Cyprus. While the published report notes that the tracker showed the location of that one vessel only, it also says that, because the ship was part of a carrier strike group sailing in the Mediterranean, knowledge of the single vessel’s location could potentially put the wider fleet at risk.
Navy discovery, disabling, and the screening gap
Navy officials reported that the tracker was discovered within 24 hours of the ship’s arrival, during mail sorting, and was eventually disabled. That discovery followed standard mail handling aboard the ship, but the incident prompted an immediate procedural response: Dutch authorities now ban electronic greeting cards on naval vessels. The published account makes a specific operational note about screening differences—packages were x-rayed before being brought on board, but electronic greeting cards were not—identifying an obvious pathway that the concealed tracker exploited.
What this means for naval mail, journalists, and adversaries
- Naval mail handlers: The incident demonstrated a screening gap tied to media of conveyance—electronic greeting cards were handled differently than packages, and that differential was exploited. Dutch authorities responded by banning electronic greeting cards from ships.
- Journalists and public experimenters: The case shows that following government-published directions can yield operationally meaningful outcomes; a journalist used those directions to stage an experiment that produced a one-day track of a naval vessel.
- Potential adversaries or opportunistic actors: The published account warns that knowing the location of one ship in a carrier strike group could potentially endanger the wider formation, making such low-cost methods of location disclosure relevant beyond a single-ship context.
The episode is compact and concrete: a publicly demonstrated technique, a documented transit from Heraklion toward Cyprus, and a swift operational correction in the form of a ban on electronic greeting cards after the device was found and disabled during mail sorting within 24 hours of arrival. It leaves a narrow but clear set of facts—the method used, the movement observed, and the procedural change enacted—while highlighting how a small device and an overlooked pathway in routine mail handling produced results significant enough to alter policy aboard Dutch naval ships.
Original story: https://www.schneier.com/blog/archives/2026/04/hiding-bluetooth-trackers-in-mail.html
