Default vendor logins and passwords are a common security issue that Nessus can scan for. Some of these default accounts can pose a serious security risk, depending on the type of access they permit. Nessus plugin id 35029 ("Dell Remote Access Controller Default password (calvin) for 'root' account") is a great example of this. It looks for a default username and password present on DRAC (Dell Remote Access Controller) devices which provide remote systems management for Dell servers.
This is a common practice for many vendors: instead of having the end user create a password during the initial configuration of the system, the vendor assigns a default value. The default passwords are often posted in the vendor's documentation, and several other web sites such as the list provided by the Phenoelit group. In this case, the default username and password pair allows a user access to the DRAC server functionality, including the ability to power the server on or off, and access the remote console. The DRAC system is an embedded system that sits inside the server with access to the hardware. It is intended for maintenance purposes and is separate from the operating system on the server.
The DRAC login and password provides access to the console as if the user were sitting in front of it. A serious risk is posed if an administrator had logged into the console as root and forgot to log off, providing the attacker with the root-level access when connecting via DRAC.
A common security requirement is to ensure that system consoles are physically protected from access. Using the default username and password for DRAC violates this requirement and poses a serious security risk.
It is important to investigate the results of each plugin and determine the full implications of the findings. Change the default passwords and be certain to log out of your sessions when administering systems (Windows or Linux/UNIX). Nessus also has several other plugins for detecting the presence of default passwords, for example on UNIX systems see the plugin category Default Unix Accounts.