The 'Paperwork Flood': How I Drowned a Bureaucrat before dinner., Sightless Scribbles
(sightlessscribbles.com)
Most faxes these days are unencrypted.
If you know how to eavesdrop, faxes are less secure than google to google email. Or if you need to be certain you zip encrypted the file, send it over, and then call with the password... Or fax the password.