A method of preventing unauthorized user access to a computer network has been developed. The method includes receiving a domain name server resolution request at the computer network from a requesting user. Next a reply to the requesting user is generated with a domain name server resolution and internet protocol address of a target device within the computer network. The reply is inspected with a network security device, where the network security device does not have an assigned internet protocol address so that it remains undetected by the requesting user. The network security device then monitors data traffic to the computer network to detect a reply from the requesting user. Once detected, the reply to the internet protocol address is intercepted with the network security device. Finally, the network security device verifies that the requesting user is authorized to access the computer network with the network security device.