TinyWall is a freeware Windows Firewall. It works in reverse, compared to the normal Windows Firewall - all outbound traffic is blocked, and you need to specifically allow traffic from .exe files you want to go online. Works well, and worth a look.
It was stated above that Daz Studio phones home, but so far as I know this is only for updates. I have all that update and telemetry stuff turned off in settings, and TinyWall does not allow Daz online - and it works fine. That said, I have not bothered with the last couple of versions (because there's no rendering speed boost and some of the UI has been changed).
In the EU and UK I believe it is legal to hack software you have purchased, to keep it running after a company or the software is defunct. Not sure about the USA, and don't rely on my fuzzy memory for legal advice. In some circumstances the defunct company's devs will, as a final act, kindly release a version that does not require that. Smith Micro's developers did that with their MotionArtist software, for instance, which was very good of them - as it is the only decent motion-comics maker. Not sure about what the laws say about a former paid user going and getting a 'cracked' version of a software (rather than doing the work themselves, to keep it running) but I imagine that such things happen.
I've never heard of specific 3D content being pulled remotely. Is it possible that the circumstance was that the content vanished from the Daz production database (and thus a library that was hooked into that) - but was actually still in the user's runtime?