Every medical practice. Their fax machine is also the usual venue hackers use to break in and steal patient records. None of those machines use encrypted anything and are typically (and foolishly) wired into the office network.
The old (unattended receive) fax machines were phone-to-paper devices that were "air-gapped". Even today most use POTs dedicated fax lines. I suppose that some are connected to the office network through VOiP. But so are all the phones with voice mail.
I am unaware of fax machines that take a received graphic image, automatically convert it via OCR and then transmit it over the office network. Maybe they exist, but I'm a bit skeptical.
Can you help me fill in the possible gaps in my knowledge with specifics such as enabling hardware or software that could be a risk.
Fax is an old technology. No question there. But I have used it in the recent past to send stuff to my lawyer, close on a timeshare or two, etc. I prefer to use DocuScan, or print/scan/send or send graphic files.