In this end-of-Master project are analysed the security of the two Bluetooth technology systems: BR/EDR and Low Energy (LE). It will be explained what Bluetooth is, how it works, which is its security architecture and which are its involved weaknesses and threats. Thus, it will also be given a sort of recommendations and countermeasures to mitigate these risks. And at the end, it will be used a Bluetooth development kit to analyse security and to show some of its weaknesses.