Microsoft® Windows® XP Unleashed

Virtual Private Networks

One important thing to understand about TCP/IP is that it wasn't developed with a great deal of security in mind. In the early days of the Internet, only large corporations, the government, and educational institutions typically were connected to the Internet. In this small community, you didn't have to worry much about hackers or computer viruses.

Today, however, the situation has changed dramatically. Since the actual data that IP carries in the payload section of its datagram is not encrypted, someone else can easily intercept it. A network adapter can be put into what is called promiscuous mode, in which case it will send all packets it detects on the network up the protocol stack for processing. Generally, only packets ...