Ubuntu Linux install and configure OpenSSH (SSHD) server

I am totally impressed with new Ubuntu Linux server. Default installation did not install any single service :)

This gives pretty good control over box. Following command returned nothing:
$ sudo netstat -tulpn

However sshd is bare minimum these days and it should be installed by default.

To install openssh server type following command:
$ sudo apt-get install openssh-server

Make sure openssh is running:
$ netstat -tulpnOutput:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp6       0      0 :::22                   :::*                    LISTEN     3458/sshd

Now we will tight openssh security. First change default 22 port to something else like 512. This will avoid automated tools login into your box:
$ sudo su -
# vi /etc/ssh/sshd_config
Find line that read as follows:
Port 22
Replace port 22 with 512:
Port 512
Save and close the file. Restart sshd:
# /etc/init.d/ssh restartOutput:

 * Restarting OpenBSD Secure Shell server... 

Finally make sure you open port 512 using iptables. Type the following command to list current firewall rules:
$ sudo iptables -L -n
Output:

Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpts:6881:6882
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:443
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0           udp dpt:514
ACCEPT     all  --  192.168.1.100        0.0.0.0/0
ACCEPT     all  --  192.168.1.101        0.0.0.0/0
ACCEPT     all  --  192.168.1.102        0.0.0.0/0
LOG        all  --  0.0.0.0/0            0.0.0.0/0           LOG flags 0 level 4
DROP       all  --  0.0.0.0/0            0.0.0.0/0           

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0

Use GUI program such as firestarter to manage and open port 22 (ssh port).
$ sudo firestarter &

Updated for accuracy.