VPN (Virtual Private Network) is a class of technology that allows remote machines to interconnect by creating a virtual network layer, on top of the physical network connection, that in practice is used to maintain the privacy of data shared over this virtual network connection (essentially all VPN toolsets use some form of packet-level encryption. There are many different modern implementations of the VPN concept itself, to the point where categorizing them together becomes somewhat questionable.
Virtual Private Networks are deployed by organizations and individuals for different purposes:
- Protecting confidential information in organizations (for example, when connecting geographically distant office networks);
- Providing "work from home" or traveling employees with secure remote access to office network resources;
- Securing general Internet traffic in particularly insecure network usage settings (e.g. open wireless networks);
- Encrypting all internet traffic to and from a home connection, to prevent ISP packet shaping and/or surveillance.
When used for Internet connectivity, VPN service also acts as a form of proxy and protects the user's real IP address from public display. As a result, they are an increasingly popular form of anonymity protection for ordinary internet users and criminals.
VPNs and anonymity
- Log files: VPN services may maintain usage logs which could then be used to track the activities of the user of those services, after the fact. However some commercial consumer-oriented VPN services specifically configure their servers not to retain any logfile information of this type. Example are Cryptocloud VPN or iVPN.
- Protocol stack: TCP timestamps and IP ID values may be used in correlating incoming (encrypted) and outgoing (unencrypted) network streams. This type of "traffic analysis" can, in theory, be used to gather information about a fully-encrypted VPN connection - in practice, there are no known public examples of traffic analysis being used against commercial VPN service providers.