#!/bin/bash
###########################################################################
##  Copyright (C) Wizardry and Steamworks 2014 - License: GNU GPLv3      ##
##  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  ##
##  rights of fair usage, the disclaimer and warranty conditions.        ##
###########################################################################

if [[ -z "$1" ]]; then
  echo "Syntax: $0 spam_domains.txt"
  exit 1
fi

DOMAIN_FILE="$1"

# Cull dead domains.
while read DOMAIN; do
  if [[ -z "$DOMAIN" ]]; then
  	continue;
  fi
  DNS_LOOKUP=`nslookup -timeout=1 -retry=0 -fail $DOMAIN | grep Name`
  if [[ ! -z "$DNS_LOOKUP" ]]; then
    echo "$DOMAIN" >> /tmp/spam_domains.txt
  fi
done < $DOMAIN_FILE

# Sort and clean
sort -u /tmp/spam_domains.txt > $DOMAIN_FILE
rm /tmp/spam_domains.txt