Hetzner do scan their networks for open proxies, spam mailing etc. They are supper aggressive on copyright too, as in you can just email them claiming an ip hosts copy right material and they will by default firewall that ip until the server owner responds.

I know this because I used to host a paste bin with them and they would constantly block my ip because people would post links to other sites that had copyright material. I didn't host anything illegal all you could post was 1mb of text. Hetzner would show me the copy right claim and it was always from some random hotmail address, the urls of the infringing material don't resolve to my ip and very clearly had nothing to do with me. Hetzner didn't care they blocked all of my servers until I had resolved the dmca request.

I had to stop using Hetzner because their blocking was too aggressive and I wasn't doing anything illegal anyway. Maybe this is self fulfilling as I would never use them for anything important after that experience, I can't risk them taking down production simply because some one with a hotmail account asked them too.