The answer to your question is good moderation and moderation tools.
I don’t know if this is quite the same thing, but @kersploosh was waging a war on bot accounts. Maybe they have some inside or can come up with something in conjunction with the admins.
Edit: that’s @kersploosh @sh.itjust.works in case the one here is someone else.
That’s me! Unfortunately, I don’t have any clever solutions to active spamming other than responsive moderation, and better mod tools whenever they become available.
I was notifying instance admins of suspicious user totals that looked like swarms of auto-created bot accounts. Last time I checked, half a dozen admins that I contacted have deleted about 250,000 suspicious dormant accounts. It’s not a solution to the problem, but it’s something.
Ban and purge.
How? I feel like it might be too easy for such accounts to be created. And they already pollute the fediverse before their accounts get banned. I think this will be more common until we have more proactive measures.