The mysterious self-booting PC: is it broken or did I mess up?

The vast majority of the time, technical problems can be primarily put down to user error. I know this. Nevertheless, this user – as in me – can’t always be asked to deal with said problems. Even less so if the error only occurs sporadically and there’s little to no negative consequences.

Here’s what happened. Most days I work from home. In doing so, I spent a few weeks wondering why my Windows PC was already running when I entered the room in the morning. This happened once or twice a week. I’d prefer some fresh bread rolls and a cup of coffee, but at least I save a few seconds that I’d otherwise lose when booting up the PC.

Now it happened twice in a row over the weekend. Once, the PC booted on Saturday when I was out for a walk. And then again on Sunday night, for the first time as I stood right next to it. I was marvelling at the starry night from my skylight in the office when a «clack» sounded from the PC next to me. Followed by a short, intense burst of fan noise and a kaleidoscope of colour under the console. The screen almost burned my retinas away with its bright light seconds later.

This heralded the beginning of my hunt for an answer, and my laziness was finally overcome.

Is it hauntings, hackers or aliens… or Wake on LAN?

Even though the computer turns on as if by magic, I couldn’t make out any mystical apparition – no ghostly fingers or anything. Likewise, I couldn’t find any suspicious processes running in the background. There is no hidden cryptomining to be discerned. No suspicious network accesses either – all is quiet.

My first thought during that late night went back to my initial suspicion I had weeks ago. However, at that time my suspicions led nowhere and I left it at this one attempt to solve the problem. When this automatic startup behaviour first happened, I considered the Wake on LAN (WOL) option. If activated in the BIOS (UEFI), a PC can be booted from other devices via the network – even via the internet if configured accordingly. The problem first occurred after I shared a folder on Windows with other devices on my network. Thus my suspicions regarding WOL. Maybe my NAS, Fritz!Box or Nvidia Shield Pro wanted access and started my PC.

No, unlikely. Especially since I never explicitly configured another network device to send the PC a so-called magic packet to wake it up. Also, the devices should only do this when I specifically want them to. Or maybe not? I’m not quite sure.

By the way, I opened the network folder to send a large file between two Windows machines for a router speed test.

Although I already did it once, I again check the UEFI of my Asus TUF Gaming Z490-Plus motherboard for whether the WOL option Power on by PCI-E is disabled. And yes, it is.

The solution: try turning on your brain

All right, let’s start from the beginning. Apart from the shared network folder, what else have I changed on the PC? Oh yeah, there’s this new network card with a 10-gigabit connection that I installed.

Slowly it dawns on me: WOL in the BIOS apparently only affects the LAN port of my motherboard, but not that of the network card.

I restart Windows 11 and go to Device Manager, which can be found in System Preferences. Then I expand the Network Adapter item and right click on my TP-Link network card (Marvell AQtion 10Gbit Network Adapter), before selecting Properties.

In the Properties, under Power Management, you’ll find «Allow this device to wake the computer». I see a check mark. And by simply unchecking it and restarting Windows, my problem is history. This process completely removes the option to start the computer via this network interface. If I want to use WOL only by Magic Packet in future, I could enable WOL again by checking «Only allow a magic packet to wake the computer». This will also solve the aforementioned enigma.

But that still doesn’t explain why my PC sporadically started itself. What other ways are there to use WOL – what’s behind it?

I keep searching and find interesting options under the Advanced tab. Some of them aren’t as self-explanatory as others. I go online to find out what they bring to the table.

There are several options that directly affect WOL. One of them is activated for me and also catches my eye in other ways. Wake on Pattern Match. If it’s enabled, apart from a Magic Packet, the PC can also be woken up by a specific connection request that wants to address the network folder, for example. According to Microsoft, Patterns refer to network packet filters that determine whether incoming network traffic should wake up the computer.

All right, the blame for this debacle can be squarely placed on my lack of knowledge. Though I do question whether it makes sense for WOL and the pattern match option to be enabled by default after installing the driver (Marvell AQtion v3.1.7).

It’s been four days since I disabled WOL for my network card in Device Manager. So far, there have been no other strange happenings in my home office. I think I squashed this bug.