Hi there.
On the lists "wikimedia-sk" and "wikimedia-sk-oznamy", where I am admin, we have received suspicious mass subscriptions (several tens in several hours). They came from nowhere, all with @
aol.com address (very unusual for our target group) and all declared only first name. Most certainly some bot.
Provisionally I have set them all for moderation. Eventually I could block subscriptions from @
aol.com addresses (no too big deal, because hardly someone real in our audience is using them) but I prefer systemic solutions and not to cure symptoms. And possibly someone else here is running into the same problem.