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Re: Anti-Spam Mail Address Encoding (with encrypted IP-Address)

by projekt21 (Friar)
on Jul 14, 2003 at 13:23 UTC ( #273970=note: print w/replies, xml ) Need Help??

in reply to Anti-Spam Mail Address Encoding (with encrypted IP-Address)

Just to add some code that can be used as is, I have written a subclass for Apache::AntiSpam by Tatsuhiko Miyagawa, that implements this method. The code is not perfect but working. I also sended this to Tatsuhiko and asked him to bundle this with his modules.

package Apache::AntiSpam::SpamTrap; use strict; use vars qw($VERSION); $VERSION = '0.01'; use Apache::AntiSpam; use Apache::Constants qw(:common); use base qw(Apache::AntiSpam); use Crypt::Blowfish; sub antispamize { my($class, $email, $orig) = @_; # this seems not very efficient my $r = Apache->request(); # better error handling? my $key = $r->dir_config('Key') || return SERVER_ERROR; my $ip = $r->get_remote_host || return SERVER_ERROR; my $time = time; my $string = spamtrap_encode($ip, $time, $key); $orig =~ s/\@/-$string\@/; return $orig; } sub spamtrap_encode { my ($ip, $time, $key) = @_; return unless $key; return unless $time > 0; return unless $ip =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/o; my $inkey = pack("H16", $key); my $plaintext = join("", map { chr } split (/\./, $ip)) . pack("L" +, $time); my $cipher = new Crypt::Blowfish $inkey; my $string = unpack("H*", $cipher->encrypt($plaintext)); return $string; } 1; __END__ =head1 NAME Apache::AntiSpam::SpamTrap - Add SpamTrap suffix to local-part in Emai +l =head1 SYNOPSIS # in httpd.conf <Location /antispam> SetHandler perl-script PerlAddVar Key 0123456789ABCDEF PerlHandler Apache::AntiSpam::SpamTrap </Location> # filter aware PerlModule Apache::Filter SetHandler perl-script PerlSetVar Filter On PerlHandler Apache::RegistryFilter Apache::AntiSpam::SpamTrap Apache +::Compress =head1 DESCRIPTION Apache::AntiSpam::SpamTrap is a subclass of Apache::AntiSpam, filter module to prevent e-mail addresses exposed as is on web pages. This module adds a Blowfish encrypted string suffix to the local-part of e-mail addresses. This string contains a timestamp and the IP address of the remote host. This enables you to identify a spammer's address harvester by its IP address and take steps to prosecute him. The encryption prevents faking and may help in a prosecuting attemp. For example, C<> will be filtered to C<>. This module is Filter aware, meaning that it can work within Apache::Filter framework without modification. You need to give the Blowfish key in your Apache configuration file. To decode a received mail's SpamTrap string use the following function +: sub spamtrap_decode { my ($string, $key) = @_; return unless $key; return unless $string =~ /[0-9a-f]{16}/o; my $inkey = pack("H16", $key); use Crypt::Blowfish; my $cipher = new Crypt::Blowfish $inkey; my $plaintext = $cipher->decrypt(pack("H*", $string)); my $time = unpack("L", substr($plaintext, 4, 4)); my $ip = join(".", map { ord } split //, substr($plaintext, 0, 4 +)); return wantarray ? ($ip, $time) : "$ip $time"; } =head1 TODO =over 4 =item * should make local address part be configured. =back =head1 AUTHOR Alex Pleiner <> - zeitform Internet Dienste 2003 This work is based on the Apache::AntiSpam::* modules provided by Tatsuhiko Miyagawa <>. The idea is taken from Daniel A. Rehbein ( This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =head1 SEE ALSO L<Apache::AntiSpam> =cut

alex pleiner <>
zeitform Internet Dienste

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