Jun 5 11:09:14 b235 in.telnetd[25273]: connect from 134.x.x.x (134.x.x.x) Jun 5 11:09:24 b235 login: FAILED LOGIN 1 FROM 134.x.x.x FOR UNKNOWN, User not known to the underlying authentication module

Like already said, all is safe. A snippet from man in.telnetd (note that all modes require authentication): SYNOPSIS /usr/sbin/in.telnetd [-hns] [-a authmode] [-D debugmode] [-L loginprg] [-S tos] [-X authtype] [-edebug] [-debug port] -a authmode This option may be used for specifying what mode should be used for authentication. Note that this option is only use- ful if telnetd has been compiled with support for authenti- cation, which is not available in the current version. The following values of authmode are understood: debug Turns on authentication debugging code. user Only allow connections when the remote user can pro- vide valid authentication information to identify the remote user, and is allowed access to the specified account without providing a password. valid Only allow connections when the remote user can pro- vide valid authentication information to identify the remote user. The login(1) command will provide any additional user verification needed if the remote user is not allowed automatic access to the specified account. other Only allow connections that supply some authentica- tion information. This option is currently not sup- ported by any of the existing authentication mecha- nisms, and is thus the same as specifying valid. none This is the default state. Authentication informa- tion is not required. If no or insufficient authen- tication information is provided, then the login(1) program will provide the necessary user verification. off This disables the authentication code. All user ver- ification will happen through the login(1) program.