How can l if someone has been on my home wifi network in the past?

I am aware of DCHP tables, and apps that can scan your network to see who is "currently" on your wifi network, but I am more interested in how to tell if someone has been on my wifi network at some point in the "past". Or if that's not possible, what can I do today to keep a running log of all devices that will have ever connected to my wifi network in the future?

I ask because I had 5-6 periodic instances where my virus scanner all of a sudden would stop working, and I cant seem to find a cause and effect. I want to rule out that my wifi is secure.

Thanks!