Blocking an IP address

For example, if a script kiddie is trying to ssh from address w.x.y.z as adam, betty, charlie, dan, ed, etc.:

iptables -I INPUT -s w.x.y.z -j DROP

The login attempts are generally harmless (unless they succeed, of course), but they can be distracting if you're debugging something related to processes (e.g., atop or ps).