Bluetooth Low Energy (BLE) Security

Bluetooth Low Energy, introduced as part of the Bluetooth 4.0 specification, is designed for short-range communication with minimal power consumption. It is ubiquitous in fitness trackers, medical devices, smart locks, beacons, and countless other IoT products. While BLE includes security provisions, its implementations frequently contain vulnerabilities that attackers can exploit.

BLE security relies heavily on the pairing process, which establishes shared encryption keys between devices. The weakest pairing method, "Just Works," provides no protection against man-in-the-middle (MITM) attacks because it performs no user authentication. Even with numeric comparison or passkey entry methods, vulnerabilities have been demonstrated. The KNOB (Key Negotiation of Bluetooth) attack forces devices to use reduced-entropy encryption keys, while the BLURtooth vulnerability allows key overwrites across BLE and Classic Bluetooth.

Common BLE attack techniques include passive eavesdropping on unencrypted advertisements and characteristics, GATT (Generic Attribute Profile) enumeration to discover exposed services and sensitive data, replay attacks using captured BLE packets, and spoofing attacks where an attacker impersonates a legitimate device. Tools like Ubertooth, BTLE-Sniffer, GATTacker, and nRF Connect facilitate BLE security testing.

Securing BLE deployments requires enforcing Secure Connections pairing (LE Secure Connections introduced in Bluetooth 4.2), implementing application-layer encryption rather than relying solely on link-layer security, minimising data exposed through GATT characteristics, randomising BLE MAC addresses to prevent tracking, and disabling unnecessary BLE services on devices when not in active use.