The Wandering Geek

Speaking of security and pen-testing, below is a Perl script I wrote and use to do bulk reverse-DNS (PTR) lookups on a specified network, during the discovery phase of a network assessment. Just cut-n-paste it into a text editor and save; instructions are in the header comments (Update: You can also download the script here) #!/usr/bin/perl # # netdns.pl: Simple script to do bulk PTR lookups on a network of IP’s # # Requires Net::DNS, NetAddr::IP # # perl -MCPAN -e ‘install Net::DNS; install NetAddr::IP’ should do the # trick on any Unix OS. On Debian/Ubuntu, do ‘apt-get install # libnet-dns-perl libnetaddr-ip-perl’ # # Usage: Takes an IP network or single IP (as per the NetAddr::IP docs # at http://search.cpan.org/~luismunoz/NetAddr-IP-3.028/IP.pm). Output # is a comma-delimited list of the IP addresses and the hostname they # resolved to, or NXDOMAIN if no PTR record exists, or if the IP # address is not well-formed, or error text if there is some other # error with the DNS query. # # Examples: # # ./netdns.pl 10.0.0.1/24 > ptr-list.csv # ./netdns.pl 10.0.0.1 # # Copyright (c) 2006, Doug Maxwell <doug@unixlore.net> # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, but # WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 # USA # use strict; use warnings; use Net::DNS; use NetAddr::IP; my $ip = new NetAddr::IP (shift) || die “Unable to create NetAddr::IP object\n”; my $res = Net::DNS::Resolver->new; my $num = $ip->num(); for (my $i=0; $i<=$num; ++$i) { my $ip_address = $ip->addr(); if ($ip_address) { my $query = $res->search(”$ip_address”); if ($query) { foreach my $rr ($query->answer) { next unless $rr->type eq “PTR”; print “$ip_address,”,$rr->ptrdname, “\n”; } } else { print “$ip_address,”,$res->errorstring,”\n”; } } ++$ip; }