Many Fediverse instances have open sign-ups without proper limits, enabling this to even happen in the first place.
Open registrations should NEVER be enabled on instances without proper protections and monitoring.
It's important to note that this attack doesn't require any novel exploit, just the existence of unmonitored, un-protected instances with open registration. From what we've seen, these are usually smaller instances.
If you must have open registrations on your instance, use the proper anti-spam and anti-bot mechanisms. We also recommend blocking sign-ups using Tor IP addresses and temporary email domains.

[–] CarbonIceDragon@pawb.social 13 points 9 months ago (3 children)

hypothetically, what stops a spam group from creating their own instance to register accounts on, or several such? It'd get defederated quickly once the attack got going, sure, but it would take time for this to get done, and in the meantime the spam gets in

[–] DoomBot5@lemmy.world 10 points 9 months ago

Why use your own resources when you can use someone else's?

[–] NicoCharrua@lemmy.ca 7 points 9 months ago

It's probably more expensive and inconvenient.

Also it might only take one report for an active mod team to ban a server. How long can that take? An hour? Less? If they're on servers that real people use, bots have to be banned one by one, so the spam can last a lot longer and reach more people.

[–] Draconic_NEO@lemmy.world 7 points 9 months ago

I don't think really anything, it just takes more effort and they'd need to change the domain every time they get blocked. I have seen a few services hosted solely for spam and bad faith practices, though they were Mastodon, Plemora, and Kbin servers, not Lemmy.