Securing SSH
ISC recommends adding the following to your sshd_config:
PermitRootLogin no
AllowUsers userA userB userC
Protocol 2
LoginGraceTime 20s
MaxStartups 5
Banner /etc/ssh/sshd_banner
My standard banner is:
Use of this network is restricted to authorized users. User activity is monitored and recorded by system personnel. Anyone using this Network expressly consents to such monitoring and recording. BE ADVISED: if possible criminal activity is detected, system records, along with certain personal information, may be provided to law enforcement officials.
[...] At this point you’re done! Couple this with using SSH keys and these sshd_config changes and you’re on your way to a secure SSH daemon. [...]
[...] Use These settings in SSHD_config to further secure SSH [...]