Stop Exception Notifications With The ZombieShotgun

I am all about knowing how to survive a zombie invasion – as much as I am a firm believer of using the right tool for a given job. It can not be argued that killing zombies with a shotgun to the head is as natural a fit as peanut butter to chocolate. They simply just go together.

Now real zombies may not be a daily nuisance, but computer zombies are a daily pain in the butt to network administrators as well as software engineers alike. If you have ever deployed a rails application into production that used some sort of exception notification, then you may at some time seen some zombie attacks throw a bunch of exceptions. My solution a few years back was to build my own ZombieShotgun module, see below.

The idea is simple, include the module and add this line to the very top of your filter chain before_filter :shoot_zombies. Just like in real life, if rails detects a zombie attack, it will issue a 404 not found error in the beautiful rails syntax head :not_found. I love it when code models the real world! Please note that there are a ton of better ways to accomplish user agent filtering, most notably, in your web server config... but that does not mean this is not a fun module to use.

module ZombieShotgun

  ZOMBIE_AGENTS       = ['Microsoft Office Protocol Discovery','Microsoft Data Access Internet Publishing Provider Protocol Discovery','FrontPage']
  ZOMBIE_ATTACK_DIRS  = ['_vti_bin','MSOffice','verify-VCNstrict','notified-VCNstrict']

  protected

  def shoot_zombies
    head :not_found if zombie_attack?
  end

  def zombie_attack?
    zombie_attack_on_directory? || zombie_agent_attack?
  end

  def zombie_attack_on_directory?
    attack = request.path.from(1)
    attack_dir = attack.index('/').nil? ? attack : attack.to(attack.index('/')-1)
    ZOMBIE_ATTACK_DIRS.include?(attack_dir)
  end

  def zombie_agent_attack?
    ua = request.env['HTTP_USER_AGENT']
    !ua.blank? && ZOMBIE_AGENTS.any? { |za| za =~ /#{ua}/ }
  end


end