Pi-hole in the smart home: Cyber security from the inside out

A while ago, I stumbled across an article by Ben Balter in which he describes how he built his home network for maximum privacy and security. The article is technically deep, well thought out – and it inspired me right away. If you know my blog, you know: something like that doesn’t leave me cold. I had to build it myself.

The result: a running Pi-hole in my network. And I’m simply thrilled.

Pi-hole is a DNS sinkhole – put simply, a small server that intercepts all DNS queries on the network and simply blocks known advertising, tracking and malware domains. Before a device can even establish a connection to a dubious domain, Pi-hole answers with a plain “No”. No request, no connection, no problem.

The beauty of it: Pi-hole works network-wide. Not just in the browser, not just on one device – but for everything connected to the network. From the smartphone to the smart TV to the light bulb.

You don’t need expensive hardware for Pi-hole. I still had an old Raspberry Pi 2 B sitting in the basement – unused for years, a bit of dust on it, but otherwise flawless. Exactly right for this use case. Pi-hole is so lightweight that even this older hardware is completely sufficient.

So that it also fits visually into my server rack, I simply printed a mount on the 3D printer. For me, that’s simply the beauty of a well-equipped home lab: you can quickly and pragmatically build solutions that really fit – in the truest sense of the word. The Pi now sits neatly and tidily in the rack, as if it had always been there.

I won’t hide the fact that the first hours after switching it on were rough. By default, Pi-hole blocks quite aggressively, and you notice that quickly when services that used to run without problems suddenly give up the ghost.

• Shelly setup: My entire Shelly infrastructure – switches, smoke detectors – suddenly stopped working. The Shellys communicate with their cloud servers, and exactly these DNS entries were blocked at first. Solution: the corresponding servers had to go on the whitelist in Pi-hole.
• Prusa printer: My Prusa printer went on strike, too. PrusaConnect and the associated cloud connection no longer got through. Here, too: whitelisting the relevant domains, and everything ran again.
• Prowlarr and Servarr: If you run an *Arr stack like I do, you’ll know this. Prowlarr and co. need to access external indexers, and exactly these indexer domains are classified as potentially dangerous and filtered by Quad9 – my chosen DNS upstream. Here, too, I had to whitelist manually.

The initial effort is real. But after this setup phase, it runs stably – and troubleshooting has become routine by now: when a service suddenly stops working, I look at the Pi-hole log first. Nine times out of ten, that’s exactly where the cause is.

After the initial teething problems, you very quickly notice why all of this was worth the effort.

1. No more ads. Really, none. Not on websites, not in apps. That sounds trivial, but the difference in everyday life is enormous. You even forget how much noise advertising actually creates – until it’s suddenly gone.
2. Websites load faster. Without ad scripts, tracking pixels and analytics calls, pages build up measurably faster. Not by seconds, but noticeably. This stands out especially on resource-hungry news sites.
3. Devices with conspicuous behavior become visible. This is perhaps the most exciting aspect. In the Pi-hole dashboard, you can see for every device on the network how many DNS queries it makes – and to whom. What surprised me most: the IoT device with by far the most queries on my network is my ambilight lighting on the TV – my Nanoleafs. A light. It makes more queries than my computer, than my phone, than my NAS. What does a lamp have to ask so much about? That’s exactly the point: without Pi-hole, I would never see this, let alone be able to question it.

It’s really amazing how much more you can get out of your network – both in terms of performance and security. After the initial configuration effort, Pi-hole now runs stably and with little maintenance for me. When a service suddenly doesn’t work the way it used to, it’s usually because its DNS connections are classified as potentially dangerous. Troubleshooting is then quite easy once you have understood the principle.

But the most important thing is the increased cyber security from the inside out. And that’s an idea that really matters to me: security in the home network isn’t limited to threats that actively come from outside. What happens when someone on the network – a guest, a family member, a poorly secured IoT device – clicks on a shady link or connects to a dubious service? With Pi-hole, this is already filtered at the DNS level, before a connection is even established.

An old Raspberry Pi, a 3D-printed case, some configuration effort – and the home network is significantly more secure and cleaner. The engineer in me is satisfied.

P.S.: Pi-hole was once again one of those open source projects I was happy to donate to. Please do the same, because that’s the only way great digital products like this can be created and run sustainably.

Inspired by: Ben Balter – Over-Engineered Home Network for Privacy and Security