If your instance has open registration, you might want to temporarily reconsider that ALONG WITH taking a close look at which remote posts are showing in the instance's public timelines.

See the conversation at https://bae.st/objects/b2f916c7-8c8b-4e30-9ac0-011343217203 for a discussion of an apparent ongoing effort to crawl and index the Fediverse, then report illegal or questionable content to #USDOJ / #FBI. (I presume that instances based elsewhere might be reported to that nation's authorities.)

There's also one or more bad actors who show up, post illegal or questionable content, then report the content to hosting companies, domain registrars, et cetera.