This is not a bad idea, though i would guess that if these guys change IPs, then it will be annoying to spend your time sneding emails, etc. But, then i thought: why not automate this with some simple scripts? You have al;ready outlined your recipe, so simply automate the steps...But the more i thought of the automation around this, you need to be creful not to turn into a "spammer of sorts, constantly sending emails...certainly, you wouild be sending legitimate emails, but if they change their IPs more often, that might trigger your automatiomn more often, somewhat turning you into a mild "spammer", right? :-) I'm not suggesting you abandon your apporoach, but simply to remember to not overdo it with big scale of emails sent out. ;-)

Aha, some more good ideas there! But you're right, there's tradeoffs and dependencies and uncertainties throughout, so it's not easy to even guess in advance what would work or be worthwhile. Plus as you say there could be negative consequences from a kind of arms-race, with the solution becoming a problem in itself.

It's not the same thing, but I'm reminded now of email in the past, when you would usually get an undeliverable message if something went wrong. But later that was almost entirely stopped - because of spam. Massive volumes of spam was sent from forged addresses, and much of it led to those replies. So that made things worse by doubling the volume, plus the innocents whose addresses had been forged got deluges of confusing undeliverable messages!

I think you're right in that changing IPs would be easy for them. But, changing hosts would be significantly more work and hassle. So if the abuse reporting worked, that could have much more of an impact...

Block all of the prefixes that their AS announces too: https://bgp.tools/as/35913#prefixes

Abuse contacts never work. I've never had any success hounding them about malicious sites they host.

I have almost no experience of this, and nothing recent, so I don't know. But I'm not surprised at what you say, given the amount of abusive stuff that happens online nowadays.

actually works very well when it's combined with DMCA takedown request.

Ah yes... Those stories we read where even a hint of a DCMA request results in a takedown, so that the host avoids the legal risk. That could be extremely effective in this case?!