Script to notify unknown device connects to LAN

[Col8eral]

Does anyone know of a script that can send a notification email when an unknown device connects to the LAN. So, if the device IP/MAC is known already then no notification is sent. Something along those lines.

 

[L&LD]

Did you search?

I recall that was discussed here before.

 

[rung]

Looks like the app will do this for you:
Link

 

[Col8eral]

Thanks guys. Much appreciated. I have set app notifications, which does work, but I would like a script to send emails if possible.

I did do a search, but didnt manage to find much. I found this script, but doesnt work on ASUS routers as far as I can tell. If there's anyone who has the skills, could this be modified to work:

#!/bin/sh
# script to detect new DHCP lease
# this will be called by dnsmasq every time a new device is connected
# with the following arguments
# $1 = add | old
# $2 = MAC address
# $3 = IP address
# $4 = device name

notification_email="####@gmail.com"
known_mac_addr="/etc/storage/known_mac_addr.txt"

# check if the MAC is in known devices list
grep -q "$2" "$known_mac_addr"
unknown_mac_addr=$?

if [ "$1" == "add" ] && [ "$unknown_mac_addr" -ne 0 ]; then
msg="New device on `nvram get system.@system[0].hostname`.`nvram get dhcp.@dnsmasq[0].domain` $*"
echo `date` $msg >> /tmp/dhcpmasq.log
# encode colon (:) and form e-mail
echo "To:"$notification_email > /tmp/email.txt
echo "From:"$notification_email >> /tmp/email.txt
echo "Subject:A new device appears in the home network" >> /tmp/email.txt
echo $msg | sed s/:/-/g >> /tmp/email.txt
sendmail "###@gmail.com" -H 'exec openssl s_client -quiet -tls1_2 -connect smtp.gmail.com:465' < /tmp/email.txt -au"####@gmail.com" -ap"pass###" -f "####@gmail.com"
fi