Servers can be backdoored by exploiting buggy motherboard controll
arstechnica.com
arstechnica.com
There's another one from a host that just has it open to the internet. I bet you'd find a bunch by scanning the internet.
I was once fired (forced to "resign") from a full-time job at a major university because I refused to rush weakening the security of a credit card processing network covered by PCI-DSS because a vendor couldn't figure out how a VPN works.
Too bad Oxide's non-BMC[0] service processor or something similar isn't available on all servers.
[0] https://oxide.computer/faq-friday/is-the-oxide-service-proce...
If you don't disable that, and sometimes even then.
Making that shit available on your general uplink.