automated nmap scans

Whipped this up for work, figured I’d share with the world, since it’s decently useful. Stick it in cron nightly, needs to run as root. It will run a diff on what it sees and email you if there are new ports/hosts that pop up on your networks. If you find errors or mods, use this: http://pastebin.com/f635a7517 to modify it and post in the comments.

#! /bin/sh

DIR="/opt/nmap/scans"
NETWORKS="192.168.1.0-255"
TODAY=`date +%Y%m%d`
YESTERDAY=`date -d yesterday +%Y%m%d`

for network in $NETWORKS
do
      nmap -n -sS $network -oG $DIR/$network.$TODAY.nmap
done

for network in $NETWORKS
do
      diff -I "^#" $DIR/$network.$TODAY.nmap $DIR/$network.$YESTERDAY.nmap  > $DIR/$network.$TODAY.diff
done

for network in $NETWORKS
do
      SIZE=`find $DIR/$network.$TODAY.diff -size +0b`
      if [ "$SIZE" = "$DIR/$network.$TODAY.diff" ]
      then
              cat $DIR/$network.$TODAY.diff | mail -s "Change Detected for $network"  user@host.com
      fi
done