Защита от подбора паролей в mod_auth

 У login`а есть фича по увеличению таймаута при вводе нескольких
   неправильных паролей - особенно не поподбираешь. По понятным причинам
   у апачевских mod_auth* такого нет. А все-таки нужно и набросал я
   скриптик для "realtime" контроля логов на атаки типа wwwhack`а.
   Может, кому сгодится. Критика приветствуется.

        #!/usr/bin/perl -w

        # httprot.pl, "request for comments" version
        # run as: tail -f /usr/local/apache/logs/access_log | ./ httprot.pl

        # Configuration starts here

        # for "combined" apache log format, unauthorized request
        my $AUTH_REQ=`^([^ ]+) ([^ ]+) ([^ ]+) \[([^\]]+)\] "([^"]+)" 401`;
        #                host   ident   user      date      request   authrequired

        my $threshold=5;        # allow $threshold unauthorized requests
        my $interval=5;         # within $interval seconds without alerting

        my $syslog_facility=`auth`;     # when alerting, use these 
        my $syslog_priority=`alert`;    # facility and priority

        # Configuration finishes here

        use strict;
        use Date::Parse;
        use Date::Format;
        use Sys::Syslog;

        my %hit=();
        my %sum=();
        my ($host,$date,$time,$request);

        openlog("httprot","pid",$syslog_facility);

        $SIG{INFO}=\&print_hit;
        $SIG{ALRM}=\&cleanup;
        alarm $interval;

        # main loop

        while(<>) {
          chomp;
          next unless /$AUTH_REQ/;

          $host=$1;
          $date=$4;
          $time=str2time($date);
          $request=$5;

          # $hit{$time}{$host} is number of bad requests from $host 
          # within second numbered $time ("unixtime")
          if(defined($hit{$time})) { $hit{$time}{$host}++; }
          else { $hit{$time}{$host}=1; }        

          # $sum{$time}{$host} is number of bad requests from $host 
          # within last $interval sec (roughly)
          if(defined($sum{$host})) { $sum{$host}++; }
          else { $sum{$host}=1; }

          &block if($sum{$host}>=$threshold);
        }

        # for testing purposes: hit Ctrl-t to see current stats
        sub print_hit {
          my $rest=alarm(0);    # avoid race condition with SIGALRM
                                # and try to reduce time leak...
          print "Current state:\n";
          my ($time,$host);
          my %list;
          foreach $time (keys(%hit)) {
            print time2str(`%x %T`,$time),":\n";
            %list=%{$hit{$time}};
            foreach $host (keys(%list)) {
              printf "\t$host: $hit{$time}->{$host}\n";
            }
          }
          print "Summary:\n";
          foreach $host (keys(%sum)) {
            print "$host: $sum{$host}\n";
          }
          alarm($rest);         # ...but will leak up to 1 second per SIGINFO
        }

        # free memory - throw away expired stats every $interval seconds
        sub cleanup {
          my ($h,$s);
          my %hosts;
          my $limit=time()-$interval;   
          foreach $s (keys(%hit)) {
            if($s<$limit) {             # entries older whan $limit have expired
              %hosts=%{$hit{$s}};
              foreach $h (keys(%hosts)) {       # correct sum when expiring stats
                $sum{$h}-=$hit{$s}->{$h};
                delete $sum{$h} unless $sum{$h}>0;      # free memory
              }
              delete $hit{$s};          # again, free memory
            }
          }
          alarm $interval;              # restart timer
        }

        # site dependent action; this example is harmless
        sub block {
          syslog($syslog_priority,
            "$sum{$host} unauthorized requests from $host, last: $request");
        }


   Атаку с одного IP ловит моментально, если через кучу быстрых прокси,
   то не поймает. Как улучшить?