How to Find Out Your Neighbor Connected to Your Wi-Fi Before They Download Their First Gigabyte

Imagine this: it's evening, you're cozy on the couch ready to watch a movie in 4K, but the video keeps buffering mercilessly. You open your router settings and see a list of ten "unknown devices" there. Sound familiar? In my experience, these "guests" tend to show up at the worst possible moment. Of course, you could manually check the router admin panel periodically, but who among us does that more than once a year?

That's where Pi.Alert comes in — an open-source "guard dog" for your home or office network. It's not just a scanner, but a full-fledged monitoring system that will raise the alarm before an uninvited guest has time to scan your network shares.

What Is Pi.Alert and Why It's Not Just nmap with a Web Interface?

The project was originally conceived as a lightweight solution for the Raspberry Pi, but over time it grew into a powerful tool that can be run on virtually any Linux server or in Docker. Its main task is monitoring LAN and Wi-Fi connections.

Unlike simple scanners, Pi.Alert keeps history. It remembers every device, its MAC address, frequency of appearances, and even the type of hardware. If a new gadget appears on the network — you get a notification. If your "always-on" device (for example, a smart camera or server) suddenly disappears from the network — you get a notification again.

What Does It Have to Offer?

Let's break down the key features that make Pi.Alert indispensable in a Home Lab:

Total device control. The system uses multiple scanning methods simultaneously: from classic arp-scan to integration with DHCP servers like Pi-hole, Mikrotik, UniFi, or Keenetic (via SNMP or API).
Web service monitoring. If you run several self-hosted services (Nextcloud, Home Assistant, Plex), Pi.Alert will check their availability over HTTP/HTTPS, monitor SSL certificate validity, and measure response times.
Foreign DHCP server detector. This is a specific but useful feature. If someone in your network accidentally (or intentionally) plugs in a router "the wrong way" and starts handing out their own IP addresses, Pi.Alert will immediately report it.
Smart notifications. Forget about checking the web panel. The project supports sending alerts via Telegram, Pushsafer, Pushover, email, and even the ntfy service.

How It Works Under the Hood

The project architecture is logical and simple, which makes it very stable:

Backend: Written in PHP and runs on a schedule via the system cron (usually every 5 minutes). It polls the network, updates the SQLite database, and sends notifications.
Frontend: A pleasant and modern interface that supports a bunch of languages, including Russian. Here you can group devices, assign them icons, view activity graphs, and even send Magic Packets to wake up computers (Wake-on-LAN).
Satellites: If you have a complex network with multiple VLANs or physically remote segments, you can install small satellite scripts that collect data locally and send it to the "main" Pi.Alert server.

Practical Use Cases: Who Is This For?

1. Home Network Security

You've set up Pi.Alert and "cleaned up" the device list, marking your phone, laptop, and TV as trusted. A week later, a message arrives in Telegram: "New device: Xiaomi-Phone." But you only have Apple devices at home. This is a great reason to change your Wi-Fi password or check if your neighbor has "dropped by for a visit."

2. Smart Home Monitoring

Smart devices tend to "drop off" the network. With Pi.Alert, you'll know that a leak sensor or camera is offline before trouble happens.

3. Developer Monitoring

If you deploy projects to a home server, Pi.Alert will check whether your container has crashed or if your Let's Encrypt SSL certificate has expired.

How to Get Started

Installation is maximally simplified. For most Debian-based systems (including Ubuntu and Raspberry Pi OS), a single command is enough:

sudo bash -c "$(wget -qLO - https://github.com/leiweibau/Pi.Alert/raw/main/install/pialert_install.sh)"

By the way, for virtualization enthusiasts there's great news: the project is officially supported in Proxmox Helper-Scripts, so you can spin it up in an LXC container in literally a couple of minutes.

Is It Worth Trying?

If you value order in your network and want to sleep soundly, knowing that not a single byte will slip past your attention — definitely yes. Pi.Alert wins you over with its simple setup and at the same time the depth of its capabilities. It's not overloaded with unnecessary features, but everything it does have works like clockwork.

The project is actively developed by the community (it's a fork of the original but abandoned Pi.Alert), regularly receives updates and new integrations. In my experience, it's one of those tools you set up once and then just enjoy the fruits of its work.

How do you monitor your network security? Do you use your router's built-in tools or trust specialized solutions? Share your experience in the comments!