That's legitimate progress.....
To help with the how/what part of your research you should look to any home network devices which might be configured to allow access from outside the local area network (i.e., through the router from the internet side)....do you have any home automation devices such as smart thermostats, light controllers, electronic door locks, etc which might have an app to allow you to access/control them using your smart phone? Do you have any Non-Apple branded networking devices on your home network other than the portal provided by AT&T / SBC Global / Lightspeed, such as IP cameras, Network Accessible Storage (NAS) hard drives, WiFi extender devices, additional access points (AP's) that might have default configurations that could open a path from the WAN side of your router to the LAN side?
Is there any software that you use which would allow you to access your computer from outside the LAN side of your network, i.e., open ports through the router?
Do you have any Windows computers on your home network?
I'm still discounting your primary computer as not being a primary suspect in this issue.
