Most companies now use fax severs which use the same SIP trunks that phone calls to the business use. Even if they are using old POTS lines the fax machines themselves are usually not in a secure area, but out in the open where anyone can walk by and pick them up.

I had to have a discussion with our cyber group that didn’t understand this and insisted that we encrypt our digital fax sever. I tried many ways to convince them that it simply was not possible to encrypt faxes when we were getting or sending faxes to random people in the general population. It really tested my patience and my ability to stretch the truth so they would drop their idiotic request.