How to secure your SSH server

To install the open-ssh serher:

# aptitude install openssh-server

To change the default port used (helps prevent automated brute force attacks):

/etc/ssh/sshd_config

Port 2222

To enable public key authentication:

RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile      %h/.ssh/authorized_keys

To disable password authentication:

# Change to no to disable tunnelled clear text passwords
PasswordAuthentication no

To restrict logins to specific users at specific hosts:

AllowUsers username@host.example.com

To restart SSH (after making any of the above changes):

/etc/init.d/ssh restart

SSH Client HOWTO

To generate an SSL key for public key authentication:

mkdir ~/.ssh
chmod 700 ~/.ssh
ssh-keygen -q -f ~/.ssh/id_rsa -t rsa

To modify the default port setting for the client (useful if your using a non-standard port on the server):

~/.ssh/config:

Host *
Port 2222

ssk-keygen -R hostname
ssk-keygen -R [ipaddress]
ssk-keygen -R [ipaddress]:port