In a modern twist on naval espionage, a Dutch warship deployed in the Mediterranean was tracked for days using a Bluetooth device costing less than a cup of coffee. The incident, which unfolded in late March 2026, has exposed new vulnerabilities in military operational security at a time when cheap consumer gadgets are increasingly being weaponized for intelligence gathering.
According to Dutch television channel Omroep Gelderland, the saga began when a Bluetooth tracking device—typically used to find misplaced keys—was attached to a postcard and sent to the Dutch air-defense frigate HNLMS Evertsen via the Dutch military’s own postal service. The device, worth about €5, was mailed from the Netherlands, routed through the Niewe Haven naval base in North Holland, flown to Crete, and finally brought aboard the Evertsen in the port of Heraklion. The frigate, valued at approximately €585 million, was docked there as part of the French aircraft carrier Charles de Gaulle’s carrier strike group, which also includes Italy’s Federico Martinego and Spain’s Cristobal Colon frigates.
The Evertsen’s deployment to the waters off Cyprus came in the wake of rising tensions in the region, including an incident involving an Iranian-made drone. But it was a decidedly low-tech threat that caught the attention of defense officials this time around. The tracker, hidden in a seemingly innocuous postcard, was able to report the ship’s movements remotely for about 24 hours. From the moment the Evertsen left Heraklion on the morning of March 27, 2026, the device transmitted its location until the vessel arrived off the coast of Cyprus on March 28, when the signal went permanently offline. The device was discovered during routine mail sorting aboard the ship.
"Adjustments have since been made," a Dutch defense ministry spokesperson told Omroep Gelderland, emphasizing that it is now forbidden to send greeting cards containing batteries to Dutch warships. The spokesperson added that the tracker was found before it could pose an operational risk: "While the ship could, therefore, have been tracked at sea, this would not have posed an operational risk." Dutch Defence Minister Dilan Yesilgoz informed parliament of the breach on April 18, 2026.
The episode underscores a growing challenge for militaries worldwide. As The Register and Tom’s Hardware reported, instructions posted by the Dutch Ministry of Defense to help families and friends communicate with sailors inadvertently opened a loophole. Electronic greeting cards, unlike packages, weren’t x-rayed before being brought aboard, giving would-be spies—or in this case, an investigative journalist—an easy way to smuggle a tracker onto a €585 million warship. Dutch journalist Just Vervaart, who orchestrated the stunt for Omroep Gelderland, was able to monitor the Evertsen’s journey in real time for about a day, simply by following the government’s own guidelines for mailing to ships.
Security experts warn that while Bluetooth trackers have a limited range—usually measured in tens or hundreds of feet—the real danger comes from the global networks that support them. As one commentator on Tom’s Hardware pointed out, "Technically the Bluetooth tracker here did nothing other than ping nearby phones. It’s the phones that then received that ping and transmitted the tracker’s ID along with coordinates to, presumably, Apple." This means that any smartphone with tracking enabled, carried by sailors or visitors, could unwittingly relay the ship’s location to the outside world. The incident has prompted some to question why personal smartphones are allowed aboard military vessels at all, given their potential to compromise sensitive operations.
It’s not the first time operational security aboard naval ships has been breached by modern technology. Just last month, a French officer aboard the Charles de Gaulle inadvertently revealed the carrier’s location by logging a jog on the fitness app Strava. The data, which appeared online, showed the ship northwest of Cyprus and south of Antalya. The French armed forces told AFP that the incident "did not comply with the current instructions" and promised corrective action. In another case from 2024, the US Navy discovered an unauthorized Starlink terminal aboard the USS Manchester, which sailors had used to access the internet while at sea—again, a seemingly benign convenience that could have serious security implications.
The Dutch government has stressed that its deployment of the Evertsen is "a limited deployment of a defensive nature, both geographically and in terms of time," as reported by De Volkskrant. Earlier in its mission, the Evertsen faced another challenge when its main naval gun was found to be inoperable. However, Commander Marcel Keveling assured the public that the ship had "sufficient alternative weapons systems" and that its primary role was air defense, not surface-level combat.
The broader lesson here is that the lines between civilian and military technology are blurring. Devices like Bluetooth trackers, designed for everyday convenience, can be exploited for surveillance and intelligence gathering. As Tom’s Hardware noted, "New technologies have always been a problem for many militaries and security forces, as seemingly innocent features like checking in on social media and posting on apps reveal personnel’s locations, schedules, and habits." For civilians, these risks may seem remote, but for military operations, they represent a serious vulnerability.
In response to the Evertsen incident, Dutch authorities have now banned electronic greeting cards from being sent to navy ships, closing the loophole that allowed the tracker to slip through. The move reflects a broader tightening of operational security procedures across NATO navies, as they grapple with the implications of ubiquitous, inexpensive tracking technology.
Still, some experts argue that the genie may already be out of the bottle. As Bluetooth trackers, smartphones, and social media become ever more integrated into daily life, militaries will need to rethink not just their mailroom protocols but the entire ecosystem of personal electronics aboard their vessels. The Evertsen case is a reminder that in the digital age, even the smallest gadget can have outsized consequences for national security.
The story of the €5 tracker and the Dutch frigate is more than a quirky footnote in naval history—it’s a wake-up call for armed forces everywhere. As technology marches forward, the challenge of keeping secrets at sea grows ever more complex.