A unique default password is a pre-configured password that is specific to a single device and often printed on a sticker on the device.
Many devices are configured with default passwords that are simple and easy to discover. If unchanged they present a serious security risk for many devices including routers, access points, switches, firewalls, embedded systems and industrial control systems (ICS). Default passwords are provided by vendors online; many websites also offer compiled lists of default passwords.
Default passwords should be changed the first time they are used but too often that security measure is overlooked. Unique default passwords can provide more security, although that depends on what type of system is used. Randomly generated unique passwords are secure, as long as they aren’t made publicly available.
Unique default passwords also make it simpler and more secure for a user to return a device to default settings. The fact that the password is printed on the device makes it easy for the owner to find it but also ensures that it should only be accessible to someone in the physical location of the hardware.
Some manufacturers have used a sequence of characters from the MAC address or subjected the MAC address to a common algorithm, which negates any security benefit because although the password is unique, it is easily discovered. In the case of a Wi-Fi access point, for example, the MAC address is broadcast, so if the password is based on that, it becomes easily available.