To the best of my knowlege the only comparible module for performing filtering and blocking of incoming HTTP requests is mod_security.

Here is a brief overview of the differences:

mod_security

Does everything that mod_ifier does. Additionally it has:

• A wider community.
• Support for Apache 1.x and Apache 2.x
• The ability to filter cookies
• The ability to allow rules to be "chained". (ie. Two or more rules must match before a request is dropped/redirected/firewalled/wahtever.)

So why choose mod_ifier? Well mod_ifier is free enough to be included in Debian GNU/Linux, and that counts for a lot!

mod_ifier

mod_ifier allows:

• Multiple matching rules:
  • Blacklisting IPs or CIDR ranges.
  • Header matching
  • CGI parameter matching (GET & POST)
  • Path matching
  • Request type matching.
  • Whitelisting IPs or CIDR ranges.
• Per-rule actions.

Of course there may be more development of the matching abilities in the future, so mod_ifier may very well catch up. Certainly I'd expect that cookie filtering would be added prior to the next release.

More rule-types could be added above that though, so please feel free to suggest things that you see as weaknesses.