While we were together my ex boyfriend had my admin password for router. It was set to default settings as I had no clue about any of this kinda stuff. I have since factory reset my router and changed admin and WiFi password, but he is still able to access it, as I noticed and screenshotted an unknown device. How is he doing this and what can I do about it?
In theory (but probably not?) he could have installed a VPN (“Virtual Private Network”), either on the router itself, or on a device connected to the router.
A VPN allows someone to connect to a private network over the internet. So for instance, I can connect to my home network from my phone, from anywhere.
However, reseting the router to factory default would have removed any VPN from the router. And changing the password would have disconnected any hidden device running VPN software, unless it was on a device you use, I guess?
Because of that, I’m inclined to believe that you’ve handled this correctly, and if I had to guess, I’d say it isn’t him - though I obviously don’t know your full situation.
Like Ansis mentioned, it’s possible that this is something benign.
If your router gives the option, maybe try looking for the MAC address of the unknown device, and block that MAC in your router. If it turns out it was something of yours, you can just unblock it. But honestly, I think you’re okay.