blcheck.sh

#!/bin/sh
# Taken originally from http://www.daemonforums.org/showthread.php?t=302
# Modified to be more unixy (aka, not have output when things are ok)

# 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

BLISTS="
    cbl.abuseat.org
    dnsbl.sorbs.net
    bl.spamcop.net
    zen.spamhaus.org
    combined.njabl.org
"

# 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

ERROR() {
  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
fi

# Assuming an IP address of 11.22.33.44 as parameter or argument

# If the IP address in $0 passes our crude regular expression check,
# the variable  ${reverse} will contain 44.33.22.11
# 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)

# -- count of times we're listed
NUMLISTS=0

# -- cycle through all the blacklists
for BL in ${BLISTS} ; do

    # use dig to lookup the name in the blacklist
    LISTED="$(dig +short -t a ${reverse}.${BL}.)"

    if [[ -n "${LISTED}" ]] ; then
        # show the reversed IP and append the name of the blacklist
        printf "%-40s" " ${reverse}.${BL}."
        echo ${LISTED}
        NUMLISTS=$(( $NUMLISTS + 1 ))
    fi
done

exit $NUMLISTS