Turn the question back, actually. Do the DDOSers even think they're achieving anything relevant, beyond being a bit annoying? .world is down from time to time, wow, how terrible. It's not like I can't log onto any other server and interact with world's channels and threads from there, only to have my posts and upvotes become globally available as soon as world is back- Oh, wait, that's exactly how it works.
The ironic part is that unless they have access to a botnet or are operating their own colo facility, they are probably paying more to run the attack than the target is.
Each instance keeps a local copy of the communities they're federated with. Users of that instance interact with the local copy, and instances communicate with each other to tell what's going on.
This means that, if .world crashes at 5PM, and you have an account on lemm.ee, you can go to lemm.ee's local copy of world->worldnews, find a thread started at 4PM, comment on it, and other lemm.ee users will see and upvote/downvote your comment.
When .world is back on at 7PM, lemm.ee will tell it: "Hey, Cold_Brew_Enema said [Thanks a lot for the gold kind stranger] and got 6 downvotes", and .world will update the thread with your comment and downvotes for users of all instances to see.
This is my understanding of how it works, and I'm not familiar with the actual code, but it seems to be close to reality.
No, you make an alt-account on a non-world instance and interact with world communities from there. The only issue is that you aren't carrying over your subscriptions and blocks unless you use a special tool, about which I don't know much.
No. It's basically like signing in at another e-mail provider. Instead of asdfasdfasdf@yahoo.com you now have asdfasdfasdf@hotmail.com and can from then on e-mail the same contacts. Just with posts, threads and comments instead of e-mail of course.
From the recent update shared, it seems like the ddos is coming from inside the hoose (ie the ddos attacker might be another lemmy instance). In other words the point of the ddos appear to be to cause people to move off of lemmy.world. so in a way it is working. A lot of people are telling people to move off lemmy.world.
People, if an instance is crumbling, sign up to another instance!
When you are able to use lemmy.world again, use lemmy2opml/lemmy_migrate (or any other tool that works, there's a list on the Awesome Lemmy Github page) to migrate your followed communities to the new instance.
You actually can, you just append @lemmy.world to the community name when accessing from another instance that's federated with lemmy.world and once lemmy.world comes back up your contributions will be there. Any instance that's federated with the instance your posting from will be able to participate in the discussion with you for that matter. The only thing you can't do with a community when the host instance is down is subscribe to it. It would still get added to your subscriptions though if you try, the hosting insurance just won't know until it comes back up and eats through the outboxes of federated instances to "catch up".
Edit
When it does come back up it'll also get any messages that are in federated outboxes as well so your posts will ultimately show up on the host instance, just posted by your alt account
From what I understand a user(Lmao/Angled) was "sub-lemmy camping" (took up thousands of popular sub names and wasn't doing anything with them) so lemmy world banned him from that instance. He had a hissy fit and "vowed revenge" and has been attempting to do as much damage to .world as he/they could since. I can't find the original post but https://old.lemmy.world/post/943832 and https://old.lemmy.world/post/1720870 has a bit of detail.
Doesn't give much on who and why, more on what/how along with dispelling some myths.
Whoever is doing it is very quickly walking through a list of expensive queries to use in their DDoS attacks. Lemmy.world is playing whack-a-mole instead of proactively rate limiting/mitigating expensive queries. It may be that all their time is spent diagnosing and fixing with none left for proactive fixes.
The fact that the attacks are evolving and always hitting expensive queries implies that it's a moderately skilled person/group familiar with the lemmy codebase.
You can speculate on motives as well as I can.
The net effect will be a more robust server and hopefully that code/knowledge is disseminated to other instances.
I really don't get the sense that Lemmy is being overwhelmed by users. Things be pretty quite in these here parts. If this kind of volume is bringing down what I thought was one of the main instances, Fediverse seems kind of doomed. I've long been worried about scalability. I've tried other instances and had issues. Each time I think should I give up or hop instances, make a new account etc. People will flock to the biggest most stable instances, but if they can't afford fancy hosting, everything starts to crumble