Opsec oopsie: Dutch navy frigate location outed by mailing it a Bluetooth tracker

Journalists tracked a Dutch navy frigate (HNLMS Evertsen) by concealing a Bluetooth tracker in mail sent through publicly documented military mail procedures. The tracker showed the ship's movements from Crete toward Cyprus before being discovered and disabled during sorting. The Dutch Ministry of Defence responded by banning greeting cards containing batteries and reviewing broader mail security procedures.