R SERVICES (512, 513 & 514)

TCP ports 512, 513, and 514 are known as “r” services, and can be misconfigured in a way that allows remote access from any host (a standard “.rhosts + +” situation). If you are prompted for an SSH key, this means the rsh-client tools have not been installed and Ubuntu is defaulting to using SSH.

# rlogin -l root