I'm gonna take this opportunity to mention LemmyAutomod, for Lemmy instance admins.

This massive spam attack was unrelenting, but it came in the form of a large number of spam posts that had a small amount of variation. Using the above tool, it really helped to catch most of the spam within seconds or minutes of being posted.

The dev is really helpful, which is good because I needed some hand-holding, but it has been a fantastic tool with this latest spam wave being the first true test of it. When the spammers started posting images of URLs instead of links, the dev added functionality to detect images that were the same or similar to a reference image.

In addition, there's also a Lemmy spam defense Matrix chat set up by Lemmy.world where instance admins post spam accounts so others can ban them on their own instances (and add them to their automod).