This script will automatically detect people listed on DNSBL and ban them.

bl.pl

#!/usr/bin/perl
use strict;
use Irssi;
use Net::DNS;
use vars qw($VERSION %IRSSI);

$VERSION = "0.0.1";
%IRSSI = (
	authors => "zmeu",
	contact => "zmeu\@whitehat.ro",
	name => "DNSBL autodetection.",
	description => "This script will automatically detect people listed on DNSBL and ban them.".
	license => "Public domain"
);

use constant {
	DNSBL => "dnsbl.dronebl.org",
	CACHETIME => 3600,
};

my %cache;

sub resolve_host($) {
	my $hostname = shift;
	return $hostname if "$hostname." =~ (/^(\d{1,3}\.){4}$/); # yes, that sucks
	my $res = Net::DNS::Resolver->new();
	my $q = $res->search($hostname, "A");
	return unless $q;
	return map { $_->address } grep { $_->type eq "A" } $q->answer;
}

sub reverse_addr($) {
	return join(".", reverse split(/\./, $_[0]));
}

sub isgot {
	my ($server, $channel, $nickname, $address) = @_;
	return unless ($nickname ne "" and $address =~ /.+@(.+)/);
	Irssi::signal_continue($server, $channel, $nickname, $address);

	my @hosts= split("\@", $address);
	my $hostname = shift;
	my $hostname = $hosts[1];

	my ($person, $channel) = split(/ /, $channel, 2);
	my ($channelname) = split(/ /, $channel, 2);

	my $witem = Irssi::window_item_find($channelname);
	if (!$witem) { $witem = Irssi::active_win(); }

	my $result = 0;
	if (exists($cache{$hostname})) {
		if (time >= $cache{$hostname}->[0]) {
			delete $cache{$hostname};
		} else {
			return $cache{$hostname}->[1];
		}
	}

	my ($ignore) = $hostname =~ m|([^./]+)\.org|;
	my ($ignore2) = $hostname =~ m|([^./]+)\.ro|;
	my ($ignore3) = $hostname =~ m|([^./]+)\.net|;
	my ($ignore4) = $hostname =~ m|([^./]+)\.in|;

	if (($ignore eq "undernet") or ($ignore2 eq "whitehat") or ($ignore3 eq "whitehat") or ($ignore4 eq "znc")) {
		# we ignore them.
	} else {
		foreach my $addr (resolve_host($hostname)) {
			if (grep /^127\.0\.0\.\d+$/, resolve_host(reverse_addr($addr).".".DNSBL)) {
				$result = 1;
				last;
			}
		}
	}
	
	$cache{$hostname} = [time+CACHETIME, $result];

	if($result eq "1") {
		$witem->command("/kb ".$channelname." ".$nickname." Stop spamming.");
	}
}

Irssi::signal_add("server event", \&isgot);