So you want to regularly check your IP(s) if they got listed on one of the many (800+ to be exact)  public blacklists (also known as DNSBL or RBL)?

Bellow, you can find a bash script that will make your life much easier. You can also make a cronjob that sends you an email with the results or simply display the results with PHP.

# Check if an IP address is listed on one of the following blacklists
# The format is chosen to make it easy to add or delete
# The shell will strip multiple whitespace
# Last updated on 20.02.2019 @


# simple shell function to show an error message and exit
#  $0  : the name of shell script, $1 is the string passed as argument
# >&2  : redirect/send the message to stderr

  echo $0 ERROR: $1 >&2
  exit 2

# -- Sanity check on parameters
[ $# -ne 1 ] && ERROR 'Please specify a single IP address'

# -- if the address consists of 4 groups of minimal 1, maximal digits, separated by '.'
# -- reverse the order
# -- if the address does not match these criteria the variable 'reverse will be empty'

reverse=$(echo $1 |
  sed -ne "s~^\([0-9]\{1,3\}\)\.\([0-9]\{1,3\}\)\.\([0-9]\{1,3\}\)\.\([0-9]\{1,3\}\)$~\4.\3.\2.\1~p")

if [ "x${reverse}" = "x" ] ; then
      ERROR  "IMHO '$1' doesn't look like a valid IP address"
      exit 1

# Assuming an IP address of as parameter or argument

# If the IP address in $0 passes our crude regular expression check,
# the variable  ${reverse} will contain
# In this case the test will be:
#   [ "x44.33.22.11" = "x" ]
# This test will fail and the program will continue

# An empty '${reverse}' means that shell argument $1 doesn't pass our simple IP address check
# In that case the test will be:
#   [ "x" = "x" ]
# This evaluates to true, so the script will call the ERROR function and quit

# -- do a reverse ( address -> name) DNS lookup
REVERSE_DNS=$(dig +short -x $1)

echo IP $1 NAME ${REVERSE_DNS:----}

# -- cycle through all the blacklists
for BL in ${BLISTS} ; do
    # show the reversed IP and append the name of the blacklist
    printf "%-60s" " ${reverse}.${BL}."

    # use dig to lookup the name in the blacklist
    #echo "$(dig +short -t a ${reverse}.${BL}. |  tr '\n' ' ')"
    LISTED="$(dig +short -t a ${reverse}.${BL}.)"
    echo ${LISTED:----}

Have questions regarding e-mail blacklists and how they work? Well, when I have more time I will surely post about it but for now, you may just leave a comment below and I will reply when I can.


  1. Ghislain

    HI Denis,
    You could make the reversed IP with something like that, which is more readable):
    reverse=$($1 | awk -F “.” ‘{print $4″.”$3″.” $2″.”$1}’)

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.