I set up friendica as my first foray on to the fediverse. It worked well, but as it turns out doesn’t work that well with Lemmy, which was my main usecase. Well whilst trying to fix DNS issues setting up a Lemmy instance instead, I noticed my DNS logs were rather full. My Unbound DNS was getting 40k requests every 10 mins to *.activitypub-troll.cf. I don’t know who or what that is, but blocking it didn’t reduce the activity. At first I thought it was something to do with Lemmy as I’d forgotten I still had Friendica running. Thankfully stopping the Friendica service reduced the DNS request back to normal.
So if you’ve set something up recently, you might want to check if there have been any consequences in your service logs
That’s about what I concluded too. I do wonder if the fediverse grows to tens / hundreds of millions of users, just how scalable the networking will be - and how susceptible to DDOS. I haven’t a detailed understanding of the communication protocols, I’ve just noticed a reasonable amount of traffic in the log files of my single user Lemmy instance.