The blog Its FOSS has 15,000 followers for its Mastodon account — which they think is causing problems:
When you share a link on Mastodon, a link preview is generated for it, right? With Mastodon being a federated platform (a part of the Fediverse), the request to generate a link preview is not generated by just one Mastodon instance. There are many instances connected to it who also initiate requests for the content almost immediately. And, this “fediverse effect” increases the load on the website’s server in a big way.
Sure, some websites may not get overwhelmed with the requests, but Mastodon does generate numerous hits, increasing the load on the server. Especially, if the link reaches a profile with more followers (and a broader network of instances)… We tried it on our Mastodon profile, and every time we shared a link, we were able to successfully make our website unresponsive or slow to load.
It’s Foss blog says they found three GitHub issues about the same problem — one from 2017, and two more from 2023. And other blogs also reported the same issue over a year ago — including software developer Michael Nordmeyer and legendary Netscape programmer Jamie Zawinski.
And back in 2022, security engineer Chris Partridge wrote:
[A] single roughly ~3KB POST to Mastodon caused servers to pull a bit of HTML and… an image. In total, 114.7 MB of data was requested from my site in just under five minutes — making for a traffic amplification of 36704:1. [Not counting the image.]
Its Foss reports Mastodon’s official position that the issue has been “moved as a milestone for a future 4.4.0 release. As things stand now, the 4.4.0 release could take a year or more (who knows?).”
They also state their opinion that the issue “should have been prioritized for a faster fix… Don’t you think as a community-powered, open-source project, it should be possible to attend to a long-standing bug, as serious as this one?”
Abstract credit: https://slashdot.org/story/428030
It is not, but a write amplification of 36704:1 is one hell of an exploitable surface.
With that same Raspberry Pi and a single 1gbit connection you could also do 333333 post requests of 3 KB in a single second made on fake accounts with preferably a fake follower on a lot of fediverse instances. That would result in those fediverse servers theoretically requesting 333333 * 114MB = ~38Gigabyte/s. At least for as long as you can keep posting new posts for a few minutes and the servers hosting still have bandwidth. DDosing with a ‘botnet’ of fediverse servers/accounts made easy!
I’m actually surprised it hasn’t been tried yet now that I think about it…
On the other hand, if the site linked would not serve garbage, and would fit like 1Mb like a normal site, then this would be only ~325mb/s, and while that’s still high, it’s not the end of the world. If it’s a site that actually puts effort into being optimized, and a request fits in ~300kb (still a lot, in my book, for what is essentially a preview, with only tiny parts of the actual content loaded), then we’re looking at 95mb/s.
If said site puts effort into making their previews reasonable, and serve ~30kb, then that’s 9mb/s. It’s 3190 in the Year of Our Lady Discord. A potato can serve that.