I'm trying to secure my Debian server, and noticed that if I type telnet myserverip port# then anyone can see my ssh version. I'm a bit worried that people can do some harm aside from that. How can I make it so that my server refuses any telnet related requests? I googled around, but most sites tell me to modify my init.d file, but there is no telnet service in the first place. I'm sure I'm misunderstanding some things about telnet and how it works so sorry if that's the case.
Disable incoming telnet connections
debian;ssh;remote;telnet
SSH is a TCP service and there is no way to realize whether the client is telnet or whatever. If you want to hide your system version and/or system architecture, you can try for instance:http://en.wikipedia.org/wiki/Port_knockingOr, it's simple to recompile openssh with your own version. AFAIR there is a header file which contains #define witch you can change. It shouldn't be difficult to find. Just grep the sources.