I believe the end game is to insert themselves into my customer list because I've found some "customers" who aren't really customers or email subscribers, and they always have my domain name included somewhere in their email address.
Is there a way I can prevent people from accessing the customer login?
I realized after watching the video again and trying it myself that what's actually happening with customer accounts disabled is that trying to submit customer info bounces the person to the home page. So this last one was actually a newsletter subscribe. Not sure how to fix that aside from checking sign-ups on a regular basis.