DIY Raspberry Pi Security System: A Simple Guide

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Security issues are becoming increasingly important. Have you ever thought about using your electronic knowledge to create a security system? For those who are interested, today’s project shares a simple security system running on Raspberry Pi.

Features of the Raspberry Pi Security System

This Raspberry Pi security system has the following features:

1) Motion detection and photo capture using a camera;

2) Notifications sent via SMS with photos;

3) Detect when at home and automatically arm or disarm (arming: entering security mode for monitoring; disarming: not monitoring);

4) Can remotely disable or check the real-time security status via SMS.

System Hardware/Software Components

To achieve the above functions, the following hardware is required:

1) Raspberry Pi with a camera interface, this project uses Raspberry Pi 1 Model A+ (can be replaced with a newer version of Raspberry Pi);

2) Raspberry Pi camera module;

3) USB Wi-Fi/WLAN adapter that supports monitor mode, this project uses an adapter based on RT5370, mainly due to their low price and easy availability;

4) The external frame is made of Makerbeam (an open-source aluminum DIY mechanical frame previously introduced in other projects), using 4 aluminum pillars of 66mm and 8 aluminum pillars of 54mm. The Raspberry Pi and camera module are fixed to the external aluminum frame with 3D printed structures.

For software, you need to use Telegram bot, an open-source, non-profit, cloud-based lightweight instant messaging software.Telegram supports clients for Android, iOS, Windows Phone, macOS, and Linux, currently with very few users in China, it is recommended to use a more common communication method.

System Operating Modes

Automatic Presence Detection

The goal of automatic presence detection is to fully automate the system, not just to arm or disarm when leaving or returning home. The simplest way to achieve this is to try to detect the mobile phones of family members. Conceptually, this is simple, but in practice, it is the most challenging part for several reasons:

1) Capturing all packets on the Wi-Fi interface consumes a lot of resources.

2) Currently, there are no high-quality 5GHz USB Wi-Fi adapters that support monitor mode. This means packet monitoring is limited to 2.4GHz, while most modern phones now use the 5GHz band.

3) Mobile phones are not always online and sending packets via Wi-Fi. Sometimes they can be offline for 15 minutes or longer.

4) Even with an accuracy of 99%, false alarms can be annoying.

After extensive testing, a method based on known mobile phone MAC addresses is used, combining active (ARP scanning) and passive (packet capturing) detection via the Wi-Fi adapter.

The MAC addresses of mobile phones are set in the configuration, and the rpi-security application uses the following filters to capture packets in monitor mode:

a) Wi-Fi probe requests from any configured MAC address; b) all packets from the configured MAC address to the host running rpi-security.

When packets are detected, the application resets the counter, and if the counter exceeds about 10 minutes, it indicates the system is armed. To eliminate many false alarms, when transitioning from armed to disarmed (or from disarmed to armed), the application performs ARP scans for each configured MAC address to ensure they are indeed online or offline. In cases where ICMP ping is very unreliable, both iOS and Android will respond to this ARP scan with 99% accuracy. By combining captured Wi-Fi probe requests and using ARP scans, the Wi-Fi frequency becomes irrelevant at this time, as phones send probe requests on both frequencies, and ARP scans can work on both frequencies as well.

Notification Items

The Telegram bot is used to send notifications with captured images. They have a good mobile app and a good API. Messages can be viewed in a browser, and messages are synchronized across devices.

If the system is armed and motion is detected, a message with the captured image will be sent to the phone from the Telegram bot. Notifications are also sent when the alarm state changes.

Remote Control

Telegram bot commands can be sent to trigger certain actions:

/disable: Disable the service until re-enabled;

/enable: Enable the service after disabling;

/status: Send a status report;

/photo: Capture and send a photo;

/gif: Capture and send a gif.

Python

The application is written in Python 3, and the following pip modules provide most of the functionality: picamera, Scapy, python-telegram-bot. The application uses multithreading to handle events asynchronously, with 4 threads:

telegram_bot: Responds to commands.

monitor_alarm_state: Arms and disarms the system.

capture_packets: Captures packets from mobile devices.

process_photos: Sends captured images via SMS.

Installation, Configuration, and Running

The interface used to connect to the WiFi network must be the same as the one that supports monitor mode.This must be the WiFi network that the mobile phone is connected to.First, install the required software packages:

Install rpi-security, reload the systemd configuration, and enable the service:

Add one or more MAC addresses, the Telegram bot API key, and any other changes to /etc/rpi-security.conf. Ensure that the camera module is enabled using raspi-config and start the service:

You need to send at least one message to the Telegram bot; otherwise, it will not be able to send messages to the phone. This way, the service can save the chat_id of the SMS. So just send the /status command.

It runs as a service and logs to syslog. To view the logs, check /var/log/syslog. There is also a debug option that logs to stdout:

root@raspberrypi:~# iw phy phy0 interface add mon0 type monitorroot@raspberrypi:~# ifconfig mon0 uproot@raspberrypi:~# rpi-security.py -d2016-05-28 14:43:30 DEBUG   rpi-security.py:73  MainThread          State file read: /var/lib/rpi-security/state.yaml2016-05-28 14:43:30 DEBUG   rpi-security.py:44  MainThread          Calculated network: 192.168.178.0/242016-05-28 14:43:41 INFO    rpi-security.py:214 monitor_alarm_state thread running2016-05-28 14:43:41 INFO    rpi-security.py:196 capture_packets     thread running2016-05-28 14:43:41 INFO    rpi-security.py:259 telegram_bot        thread running2016-05-28 14:43:41 INFO    rpi-security.py:154 process_photos      thread running2016-05-28 14:43:43 INFO    rpi-security.py:392 MainThread          rpi-security running2016-05-28 14:43:43 INFO    rpi-security.py:112 MainThread          Telegram message Sent: "rpi-security running"2016-05-28 14:44:29 DEBUG   rpi-security.py:191 capture_packets     Packet detected from aa:aa:aa:bb:bb:bb2016-05-28 14:44:29 DEBUG   rpi-security.py:191 capture_packets     Packet detected from aa:aa:aa:bb:bb:bb2016-05-28 14:44:48 DEBUG   rpi-security.py:280 Dummy-1             Motion detected but current_state is: disarmed

All the configurations required for the Raspberry Pi Model A+ are above.Below is the layout of the WLAN network devices:

You can use interfaces with different names, just ensure to change the network_interface parameter in /etc/rpi-security.conf and the reference to mon0 in rpi-security.service.

Restart After Losing Connection

My Raspberry Pi loses WLAN connection about every month or two. I created a cron job to check connectivity and restart if the check fails.

Project Source: hackster.io

Creator: Max Williams

Compiled by: Wang Tongxue

END

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