How to deny Lan resource access to non authorized computer

We are a small company using Cisco VPn for remote users, one user copied the Cisco profile from his PC and was able to connect to our network with his personal MAC laptop, we are using Domain authentication. Is it possible to block unauthorized computers from connecting to the VPN. i see this as a problem since any user that has an AD account could simply install cisco VPN software on their home pcs and connect to our resources with any computer.