ESP32 Wi-Fi Device Sniffer

An ESP32-WROOM-based Wi-Fi Device Sniffer that passively detects nearby devices by capturing their MAC addresses and signal strength (RSSI) using promiscuous mode.

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🔧 Features

• Detects devices broadcasting on 2.4GHz Wi-Fi
• Displays MAC address, RSSI, and last seen time
• Uses ESP32's hardware promiscuous mode
• Optional button to display all detected devices
• Works offline without connecting to any Wi-Fi network

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📦 Requirements

• ESP32-WROOM board
• Arduino IDE with ESP32 board support
• Micro USB cable

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🛠 Wiring

ESP32 Pin	Purpose
GPIO0	Display button (BOOT)
GND	Button GND side

Optional: You can connect a push button between GPIO0 and GND to print the list of detected devices.

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📲 Installation

1. Install Arduino IDE

2. Add ESP32 board support via Board Manager:

   • Board URL: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

3. Install the following libraries (should be built-in):

   • WiFi.h
   • esp_wifi.h

4. Upload the sketch to your ESP32 board

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▶️ How It Works

• ESP32 is set to WIFI_MODE_NULL to disable connections
• Promiscuous mode is enabled to capture all Wi-Fi packets
• MAC addresses from management frames are extracted
• Detected devices are stored in a list with their RSSI
• Pressing GPIO0 (BOOT) prints the current device list

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🧪 Example Output

🚀 Starting WiFi sniffer...
[NEW] 92:14:36:FA:B2:77 RSSI: -45
[NEW] D8:BC:38:49:A1:CC RSSI: -70
📋 Known devices:
  92:14:36:FA:B2:77 RSSI: -45 Last seen: 5 sec ago
  D8:BC:38:49:A1:CC RSSI: -70 Last seen: 10 sec ago

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⚠️ Limitations

• Only captures devices using 2.4GHz Wi-Fi
• MAC randomization by modern phones may affect accuracy
• Does not decode payloads or establish connections
• Locked to a specific channel (default: 6)

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💡 Future Ideas

• Channel hopping to capture on all Wi-Fi channels
• Web server to view devices on a browser
• Logging to SD card or serial monitor

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📄 License

MIT License. Free to use and modify.

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Contributions welcome!