Offensive Bluetooth Classic

Bluetooth Classic (BR/EDR) Attacks

Older than BLE, less commonly attacked today, but still present in cars, industrial sensors, audio gear, and legacy enterprise hardware. Many of the well-known historic attacks (BlueSnarf, BlueBug) are mitigated; KNOB and the BlueBorne family remain relevant against unpatched devices.

Quick Workflow

1. Discover devices with hcitool / bluetoothctl / redfang 2. Enumerate exposed services via SDP 3. Test each service profile for unauth access 4. Check pairing crypto (KNOB applicability) 5. Proximity-physical attacks for legacy / unpatched

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Discovery

# Modern adapter (built-in or USB Bluetooth 4.0+)
sudo hciconfig hci0 up
sudo hcitool inq                       # inquiry
sudo hcitool scan --length=12          # 12-second scan

# bluetoothctl interactive
bluetoothctl
> scan on
> devices

# Discoverable-mode-only devices appear; non-discoverable need address brute
sudo redfang -r 00:00:00:00:00:00-FF:FF:FF:FF:FF:FF
# (very slow — ~7 hours per OUI prefix)

Service Discovery (SDP)

# List all services on a device
sdptool browse AA:BB:CC:DD:EE:FF
sdptool records AA:BB:CC:DD:EE:FF

Common profiles and their attack relevance:

SPP Abuse

The Serial Port Profile (SPP) tunnels arbitrary data over Bluetooth as a virtual COM port. Industrial / IoT devices use it for debug or telemetry, often without authentication.

# Connect to SPP service, channel typically 1
sudo rfcomm bind /dev/rfcomm0 AA:BB:CC:DD:EE:FF 1
sudo screen /dev/rfcomm0 9600
# Then interact with the device's CLI / debug menu

KNOB (CVE-2019-9506)

Forces Bluetooth pairing to negotiate a 1-byte encryption key — making the link key trivially brute-forceable.

# Test with internalblue (requires Broadcom firmware patch)
git clone https://github.com/seemoo-lab/internalblue
internalblue
> log keys
# Patch firmware to allow 1-byte key; pair with target; observe weak key

Patched in firmware on most modern devices. Still works against:

• Older Broadcom-based devices (pre-2019 BCM chipsets)
• Embedded automotive Bluetooth stacks
• Cheap consumer audio gear

BlueBorne (CVE-2017-1000251 et al.)

A family of buffer overflows / info leaks in major Bluetooth stacks (Linux BlueZ, Android, Windows, iOS). Mostly patched 2017–2018, but unpatched embedded Linux devices are common.

# Armis blueborne-scanner — checks for patch-level
git clone https://github.com/ArmisSecurity/blueborne
python blueborne_scanner.py AA:BB:CC:DD:EE:FF

HID Spoofing (PoC)

If pairing succeeds via Just Works or weak PIN, you can register as a HID device — keystroke injection on an unattended Bluetooth-paired host.

# bdaddr + HID example — register custom HID on rfcomm
hcitool dev
hciconfig hci0 class 0x000540   # HID device class
sdptool add HID
# Use a HID descriptor crafted as keyboard, send keystrokes

Audio Eavesdropping

If a target has Bluetooth headset paired and active, and you can re-pair (PIN brute or KNOB):

• HSP/HFP profiles let you become the peer and receive audio
• Some firmware allows simultaneous peer connections — eavesdrop without disrupting

Engagement Cheatsheet

# 1. Discover
sudo hcitool inq

# 2. Enumerate services per device
sdptool browse <MAC>

# 3. SPP (industrial/IoT) — connect and explore
sudo rfcomm bind /dev/rfcomm0 <MAC> 1
sudo screen /dev/rfcomm0 9600

# 4. Patch-level scan
python blueborne_scanner.py <MAC>

# 5. KNOB testing (with adapter that supports internalblue)
internalblue → log keys → re-pair target

# 6. Document profiles, auth state, exposed commands per device

Detection

• No native Bluetooth Classic IDS in most environments
• Active inquiry visible to nearby Bluetooth-aware monitoring (rare)
• Re-pairing prompts on target devices may surface to users

Reporting

• Identify chipset + firmware version per device (often visible in service records)
• Map CVE applicability (BlueBorne, KNOB, BlueFrag, et al.)
• Document specific profile abuses (SPP exposed without auth, HID spoofing successful, etc.)

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Key References

• internalblue: github.com/seemoo-lab/internalblue
• KNOB attack: knobattack.com
• BlueBorne: armis.com/blueborne
• Bluetooth Core Spec — Volume 2 (BR/EDR Controller)
• Source: https://github.com/SnailSploit/offensive-checklist/blob/main/wireless.md