Hello,
i have some troubles with someone who keeps posting porno links on my website 
I warned him because of it but since he only seems to like the attention i wanted to give him an IP ban. Anyone knows how i can place an IP ban with telnet on my unix server?
If you are using inetd to launch your tcpd processes, you can use the /etc/hosts.deny file.
The question is though, if the person shouldn't be able to log in, why not disable the account? Most likely he either has now or could easily get a dial-up account where the IP changes. That won't be easy to keep up with...
We don't have a system that allows users to register although we are working on it. There is no /etc/hosts.deny dir on our server, any other suggestions?
I found out that he always has the same ip adress so he probably uses cable or something like that.
Block him at your firewall based on IP. If you are running a publically accessible server you should definitely have a firewall...