What security vulnerabilities are addressed by VPN?
VPNs directly protect the privacy of a communication, and indirectly provide an authentication mechanism for a gateway, site, computer, or individual. Whether you need privacy or not is a function of your business, the nature of what you discuss electronically, and how much it is worth to someone else. Authentication is a side effect, even without IPSEC, because if site A knows it talks to site B over an encrypted channel, and someone else pretends to be site B, they will also have to be able to talk encrypted to site A, since site A expects it and will reciprocate. Typically, the secrets are sufficiently protected that no one could pretend to be site B and pull it off. Again, it comes down to the risk, which is a function of the information you are transmitting. The threats and vulnerabilities are there, in any case. It is very easy to capture traffic on the Internet or on your phone line. Is it important enough information to care? That is the question that most people answer wrong.
