Microsoft Corp. encourages its employees to "RAS" into the corporate network from home or from the road to access e-mail, shared files and applications. RAS stands for Remote Access Services. RAS is an old Microsoft term, now described and known as a client VPN. Within Microsoft's very vulnerable environment, VPN connections might cause some important security risks to materialize. This article offers an in depth answer to the question:
How does microsoft protect itself against security risks while continuing to offer VPN access to remote employees and contractors?
A simple summation and answer to this question, is that it requires two forms of authentification from it's users: Hardware authentification through access cards, and network access. And, the network connection has many requirements from the computer (external device...VPN Access) attempting to access it. To read the entire in depth analysis of Microsoft's security infrastructure:
How Microsoft Fights off 100,000 attacks per month--How Microsoft Protects itself from Hackers and other Security Threats