Android Nexmon Setup

Android NexMon Setup: Monitor Mode & Packet Injection

This skill guides you through enabling 802.11 monitor mode and frame injection on Android devices with Broadcom/Cypress Wi-Fi chipsets using the NexMon framework. This eliminates the need for external USB adapters by patching the proprietary firmware.

What This Skill Does

• Verifies device compatibility with NexMon
• Guides Magisk module installation
• Configures Hijacker for automated monitor mode
• Shows manual command-line alternatives
• Integrates with Kali NetHunter chroot
• Provides troubleshooting for common issues

Quick Start

If you already have a compatible device and just need the commands:

# Enable monitor + injection
svc wifi disable && ifconfig wlan0 up && nexutil -s0x613 -i -v2

# Disable and return to normal Wi-Fi
nexutil -m0 && svc wifi enable

Step 1: Verify Device Compatibility

NexMon only works with specific Broadcom/Cypress chipsets. Check your device:

# Method 1: Check via dmesg (requires root)
dmesg | grep -i bcm

# Method 2: Check via sysfs
cat /sys/kernel/debug/bcmdhd/ver

# Method 3: Use the helper script
./scripts/check_compatibility.sh

Supported chipsets:

• BCM4358 (Nexus 6P, Pixel 1)
• BCM4359 (Galaxy S7/S8)
• BCM43596 (Galaxy S9/S10)
• BCM4375B1 (Galaxy S10+)
• BCM43752 (Galaxy S20 series)

Supported devices with public patches:

• Samsung Galaxy S7, S8, S9, S10, S10+
• Google Pixel 1, Pixel XL
• Nexus 6P
• OnePlus 5, 5T, 6

If your device isn't listed, you may need to compile a custom patch from the NexMon source.

Step 2: Prerequisites Checklist

Before proceeding, ensure you have:

• Root with Magisk ≥ 24

  magisk --version
  

• BusyBox installed (most ROMs/NetHunter include this)

  which busybox
  

• NexMon Magisk ZIP for your exact device/firmware

  • Download from: https://github.com/seemoo-lab/nexmon
  • Or use pre-built: https://github.com/SpaceNinja/nexmon

• Hijacker app ≥ 1.7 (arm/arm64)

  • Download: https://github.com/chrisk44/Hijacker
  • Install the APK on your device

• (Optional) Kali NetHunter or Linux chroot for advanced tools

Step 3: Flash the NexMon Magisk Module

Installation Steps

1. Download the ZIP for your exact device/firmware combination

   • Example: nexmon-s10.zip for Galaxy S10
   • Place in /sdcard/Download/

2. Install via Magisk

   # Open Magisk app → Modules → Install from storage
   # Select the ZIP and reboot
   

3. Verify installation

   # Check libnexmon.so location
   ls -lZ $(find / -name libnexmon.so 2>/dev/null)
   
   # Verify nexutil is present
   which nexutil
   sha1sum $(which nexutil)
   

   Expected output:

   /data/adb/modules/nexmon/lib64/libnexmon.so
   /system/xbin/nexutil
   

What the Module Does

The Magisk module:

• Copies libnexmon.so to /data/adb/modules/<module>/lib*/
• Installs nexutil CLI helper to /system/xbin/
• Sets correct SELinux labels
• Preloads the library into the Wi-Fi driver

Step 4: Configure Hijacker (Recommended)

Hijacker automates monitor mode toggling before running tools like airodump-ng or wifite.

Configuration Steps

1. Open Hijacker → Settings → Advanced

2. Add these entries (adjust library path if needed):

   Prefix:

   LD_PRELOAD=/data/user/0/com.hijacker/files/lib/libnexmon.so
   

   Enable monitor mode:

   svc wifi disable; ifconfig wlan0 up; nexutil -s0x613 -i -v2
   

   Disable monitor mode:

   nexutil -m0; svc wifi enable
   

3. Enable "Start monitor mode on airodump start"

4. Create required directory (if Hijacker shows errors):

   mkdir -p /storage/emulated/0/Hijacker
   

Understanding the nexutil Flags

Test the Configuration

After configuration, run:

airodump-ng --band abg wlan0

You should see raw 802.11 frames with radiotap headers.

Step 5: Manual Mode (Without Hijacker)

If you prefer command-line control or Hijacker isn't available:

Enable Monitor + Injection

# Disable Android Wi-Fi service (required!)
svc wifi disable

# Bring interface up
ifconfig wlan0 up

# Enable monitor mode + frame injection
nexutil -s0x613 -i -v2

# Verify
iwconfig wlan0

Disable and Return to Normal

# Restore managed mode
nexutil -m0

# Re-enable Wi-Fi service
svc wifi enable

Passive Sniffing Only

If you only need to capture (no injection):

svc wifi disable && ifconfig wlan0 up && nexutil -i -v2

Step 6: Kali NetHunter Integration

Stock Kali tools don't know about NexMon. Force them to use it via LD_PRELOAD.

Setup Steps

1. Copy the shared object into the chroot:

   # From Android host
   cp /sdcard/Download/kalilibnexmon.so <chroot>/lib/
   

2. Enable monitor mode from Android host:

   svc wifi disable && ifconfig wlan0 up && nexutil -s0x613 -i -v2
   

3. Launch tools inside Kali with preload:

   sudo su
   export LD_PRELOAD=/lib/kalilibnexmon.so
   
   # Now run any wireless tool
   wifite -i wlan0
   aircrack-ng --help
   mdk4 wlan0 d
   

4. When finished, disable on Android:

   nexutil -m0 && svc wifi enable
   

Why This Works

The firmware handles radiotap injection at the driver level, so user-space tools behave like they're using an external Atheros adapter.

Step 7: Common Attack Patterns

Once monitor + TX is active, you can perform:

Capture WPA Handshakes

# Using wifite (automated)
wifite -i wlan0

# Using airodump-ng (manual)
airodump-ng --band abg --bssid <target> --channel <ch> -w capture wlan0

Capture PMKID (No Client Required)

hcxdumptool -i wlan0 --enable-status-page --allow-own-traffic

Deauthentication Attacks

# Force clients to reconnect
mdk4 wlan0 d -t <target_bssid> -c <channel>

# Or with aireplay-ng
aireplay-ng --deauth 10 -a <target_bssid> wlan0

Rogue AP / KARMA Attacks

# Create evil twin
hostapd -C /tmp/evil.conf

# KARMA attack (respond to all probe requests)
mdk4 wlan0 a

Performance Expectations

On Galaxy S10 (BCM4375B1):

• TX power: ~20 dBm
• RX rate: 2-3 M pps
• Comparable to external USB NICs

Troubleshooting

"Device or resource busy"

Cause: Android Wi-Fi service is still running.

Fix:

svc wifi disable
# Then retry nexutil commands

"nexutil: ioctl(PRIV_MAGIC) failed"

Cause: Library is not pre-loaded.

Fix:

# Check LD_PRELOAD is set
export LD_PRELOAD=/data/adb/modules/nexmon/lib64/libnexmon.so

# Or verify installation
ls -lZ $(find / -name libnexmon.so 2>/dev/null)

Frame injection works but no packets captured

Cause: ROM hard-blocks certain channels.

Fix:

# Try explicit channel
nexutil -c <channel>

# Or use iwconfig
iwconfig wlan0 channel <n>

SELinux blocking library

Cause: SELinux in Enforcing mode.

Fix:

# Option 1: Set to Permissive (temporary)
setenforce 0

# Option 2: Fix module context
chcon u:object_r:system_lib_file:s0 libnexmon.so

Monitor mode won't enable

Cause: Interface is in use or driver issue.

Fix:

# Kill any processes using wlan0
fuser -v /dev/wlan0

# Restart Wi-Fi service
svc wifi disable
svc wifi enable

# Then try again
svc wifi disable && ifconfig wlan0 up && nexutil -s0x613 -i -v2

Verification Commands

Use these to confirm everything is working:

# Check monitor mode is active
iwconfig wlan0 | grep -i mode
# Should show: Mode:Monitor

# Test frame injection
aireplay-ng --test wlan0
# Should show: Injection is working!

# Verify firmware version
nexutil -v2
# Should print firmware version and confirmation

# Run the verification script
./scripts/verify_installation.sh

References

• NexMon – firmware patching framework
• Hijacker (aircrack-ng GUI for Android)
• Kali NetHunter
• HackTricks – Android Pentesting

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