SSHD, Secure Shell Daemon (Server)

SSHD

The sshd server installation on most GNU/Linux systems is created by OpenSSH. It provides a secure protocol for connecting to your machine from a remote location.

If you want to know how to setup an SSH server on Windows XP, it has been documented here.

In linux, to only allow certain users (by default it allows any user with an account to connect), modify your /etc/ssh/sshd_config file, add the following line:

AllowUsers user1 user2

You can also not allow users to login (root for example):

DenyUsers root

I would also recommend changing the standard port (to avoid random scans from the internet), note that you will need to specify this same port when connecting remotely (for example ssh -p 3333 RemoteURLorIP); uncomment the "Port" line and change the port:

Port 3333

Then restart sshd:

Slackware:

/etc/rc.d/rc.sshd stop
/etc/rc.d/rc.sshd start
    

Redhat:

service sshd restart
    

Ubuntu:

sudo /etc/init.d/ssh restart