Traditional fax machines are insecure in two primary ways. First, they are physically vulnerable. This means that fax machines are generally located in accessible places in the workplace and almost anyone can access them. Outbound faxing can include sensitive business documents or other inappropriate material that could become a liability to a company. Knowing how to secure a fax machine would therefore seem to be in the interests of most businesses. Even if the fax machine stores a copy of each fax, such information can often be reviewed too late, after damage has been done.
Fax machines are very easy to use. Even when a fax machine is connected to a phone system that requires that an account code, such codes are often just two or three digits long and can easily be guessed. This means that--while extreme security measures on the local network prevent its unauthorized use--virtually anyone can use the fax machine to send information out of the workplace.
Inbound faxing is even more of a security issue. Because many companies have only one fax number, everything from junk faxes to legal documents arrive in a single inbox. This means that confidential personal and business information can easily be seen and read by anyone who happens to rummage through the trademark pile of incoming faxes that lie next to many fax machines.
A person may not have the will or the desire to hack into various email accounts within the company for fear of being caught, but a malicious or nosy individual can often find out incredible details about people and businesses just by hanging out near the fax machine.
The other way a fax machine is vulnerable is its transmission medium: an ordinary telephone line. This means that at any part of the circuit, the line can be tapped, allowing someone to capture all inbound and outbound faxes from a location without ever being detected.