Currently we give Internet access using ip address in our firewall script as follows
iptables -t nat -A POSTROUNTING -s 192.168.1.40 -j MASQUERADE
But we have noticed that some guys steal these ip addresses after office hours to browse personal stuff.
To make these things bit more difficult, I want to grant permissions using MAC address. So these people will find new way to break the system and will learn more about networking.