Blocking based on IP
--------------------

You can also block (or admit) users based on their incoming IP address: 
  <IfModule mod_rewrite.c>
    RewriteEngine   on
    RewriteMap      block dbm:/www/conf/my.block
    RewriteCond     ${block:%{REMOTE_ADDR}|OK}           !^OK$
    RewriteRule     ^/.*     http://%{REMOTE_ADDR}/      [L]
  </IfModule>

You create my.block.db from a file (named blocklist) that looks like this: 
    123.123.123.123    block
    123.123.123.134    block
    321.321.321.222    block
    ...

and piping it to this file: 

./db_create my.block.db < blocklist

You can add additional entries on the fly: 

echo "111.222.221.111 block" | ./db_create