Vulnerabilities in network printers have been known about for years but many people are still unaware of the risks. This is surprising bearing in mind that junk faxes were widespread in the late 1980s, as a result of the proliferation of relatively inexpensive fax machines and the development of the computer-based fax board which provided an efficient mechanism for reaching those devices with minimal cost and effort.
Most organisations probably do not need their printers to be connected to the Internet so network administrators should ensure that they disable any printer settings that allow direct access to devices over the Internet. In addition, they should change the default username and password values and close access to ports 9100, 515, and 721–731; printers will still be accessible, where they are needed, through the local network. Finally, turn off printers when they are not in use.
Researchers Hijack 28,000 Printers to Show How Easily They Can Be Hacked