A slightly different strategy, with slightly different tools: I was blocking for up to 4 hours all the noticed spammers, using this script: 
#!/usr/bin/env perl
use strict;
$|++;

my $MYDOOM = "/home/merlyn/mydoom";
my $MYSOBIGF = "/home/merlyn/sobig.f";
my $HOURS = 4;

sub now {
  my @now = localtime;
  sprintf "%02d-%02d %02d:%02d:%02d", $now[4]+1, @now[3,2,1,0];
}

use POE qw(Wheel::FollowTail Filter::Line);

POE::Session->create
  (inline_states =>
   {_start => sub {
      my($kernel) = @_[KERNEL];
      $kernel->yield("initialize_ip_list");
    },
    initialize_ip_list => sub {
      my ($kernel, $heap) = @_[KERNEL, HEAP];
      @{$heap->{ip_list}} = `pfctl -t spammers -T show` =~ /(\S+)/g;
      $kernel->yield("start_tailing");
      $kernel->yield("unblock_an_address");
    },
    start_tailing => sub {
      my($kernel, $heap) = @_[KERNEL, HEAP];
      $heap->{tailer} = POE::Wheel::FollowTail->new
        (Filename => $MYDOOM,
         Filter => POE::Filter::Line->new
         (InputRegexp => qr/(?<=\n)(?=[^ \t])/),
         InputEvent => 'tailer_got_line',
        );
      $heap->{tailer2} = POE::Wheel::FollowTail->new
        (Filename => $MYSOBIGF,
         Filter => POE::Filter::Line->new
         (InputRegexp => qr/(?<=\n)(?=[^ \t])/),
         InputEvent => 'tailer_got_line',
        );
    },
    tailer_got_line => sub {
      my($heap, $line) = @_[HEAP,ARG0];
      my ($name, $ip) = $line =~ /\((\S+)\s+\[([\d.]+)\]\)\s+by blue\.
+stonehenge\.com/ or return;
      return if $ip eq "127.0.0.1";
      print now(), ": BLOCKING $ip ($name): ";
      system "pfctl -t spammers -T add $ip";
      push @{$heap->{ip_list}}, $ip;
    },
    unblock_an_address => sub {
      my($kernel, $heap, $state) = @_[KERNEL, HEAP, STATE];
      my $ip_list_ref = $heap->{ip_list};
      if (my $ip = shift @$ip_list_ref) {
        print now(), ": UNBLOCKING $ip: ";
        system "pfctl -t spammers -T delete $ip";
      }
      my $delay = @$ip_list_ref ? 60*60*$HOURS / @$ip_list_ref : 10;
      $delay = 1 if $delay < 1;
      $delay = 60 if $delay > 60;
      $kernel->delay($state, $delay);
    },
   });
   

POE::Kernel->run;

[download]
Of course, the parts about what files to look for, what patterns to look for, and what commands to execute to disable and enable are all different, but maybe the design can be reused.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re: Firewalling brute-force spam attacks by merlyn
in thread Firewalling brute-force spam attacks by hacker

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.