UPDATE 10/4 6:47 EDT

I have been going through all the comments. THANKS!!! I did not know about the techniques listed, so they are extremely helpful. Sorry for the slow update. As I mentioned below, I got behind with this yesterday so work cut into my evening.

I ran a port scan. The first syntax, -p, brought no joy. The nmap software itself suggested changing to -Pn. That brought an interesting response:

nmap -Pn 1-9999 <Local IP Addr>

Starting Nmap 7.93 ( https://nmap.org ) at 2024-10-04 11:44 BST Failed to resolve “1-9999”. Nmap scan report for <Local IP Address> Host is up (0.070s latency). All 1000 scanned ports on 192.168.0.46 are in ignored states. Not shown: 990 filtered tcp ports (no-response), 10 filtered tcp ports (host-unreach)

Nmap done: 1 IP address (1 host up) scanned in 6.03 seconds

Just to be absolutely sure, I turned off my work computer (the only windows box on my network) and reran the same syntax with the same results.

As I read this, there is definitely something on my network running windows that is not showing up on the DHCP.

  • OfficerBribe@lemm.ee
    1·
    10 hours ago

    Besides the MAC lookup suggestion, have you tried to simply find hostname in local DNS by reverse IP lookup, maybe that would shed some light.

    Not sure if there is anything useful, but in browser just check site source, maybe there is something useful there that could help with identification. Does site have certificate? It might include info that would help with identification. Do the standard browser network trace via dev tools F12, maybe something useful appears there.

    In nmap you can attempt to guess OS, try that. Additionally it might be possible to get hostname as well.

    And have you checked your router to see if this connection is connected to your Wi-Fi AP or Ethernet to narrow things down? If it is not possible to determine this from router, simply connect your main PC to Ethernet, disable AP in router settings and check if IIS site is still up. If it is not, enable AP again, does it come back early or it takes some time?

    Lastly, if it still is a mystery, start powering off devices one by one to find the source. Based on comments it seems you have multiple devices, but I assume it would not take that long?