In most cases, when users are presented with the warning prompt stating '[App name] will damage your computer' it signals the presence of adware, browser hijackers, or another type of PUP (Potentially Unwanted Program) on their Mac system. This measure is part of Apple's efforts to stem the tide of PUPs being spread in its ecosystem. Sometimes, however, the same warning prompt may be triggered due to outdated or revoked software and driver licenses of otherwise legitimate applications. Users seeing the 'fax.backend Will Damage Your Computer' prompt shouldn't panic as it is caused by revoked licenses of older HP printer drivers.
According to an official statement released by HP, the company unintentionally removed the license for older Mac drivers resulting in users experiencing serious interruptions or being outright unable to print documents with certain HP printer models. As a stop-gap measure, HP recommended that affected users should uninstall the driver and instead rely on the AirPrint driver that comes built-in with macOS. A final patch addressing the issue was released with version 5.1 of the HP Printer Software.