R-services (rshell, rlogin) (513,514 TCP)

R-services (rshell, rlogin) (513,514 TCP)
The R-services has used in the good old days of (campus) wide open Unix clusters of machines. It was used to hop from one server to the next with as little as possible effort - it's almost the same as telnet or SSH - it gives you a shell (or executing a command). Nowadays it is not very common to find Unix servers with rlogin or rshell ports open. Rshell is basically an extension of rlogin - Rshell will execute a command after logging in with the username and password specified. For the purposes of this document we can see rlogin and rsh as the same. These two services are protected by the ".rhosts" file(s). These files reside in a user directory and contain the IP numbers (or DNS names) and usernames on the remote machines that could assume control on the local machine.
But heck - I am not here to explain how rlogin and rsh works - the only thing that needs to be said here is that you could also try to get into a machine using it. It works much the same as telnet - all the same principles apply- try getting usernames etc. Sometimes rlogin is used in conjunction with other tricks - if you can get a "+ +" (allow anyone from anywhere) in the .rhost file you are made - see the X11 section.