Tor is a toolset for a wide range of organizations and people that want to improve their safety and security on the Internet. Using Tor can help you anonymize web browsing and publishing, instant messaging, IRC, SSH, and other applications that use the TCP protocol. Tor also provides a platform on which software developers can build new applications with built-in anonymity, safety, and privacy features.
Tor aims to defend against traffic analysis, a form of network surveillance that threatens personal anonymity and privacy, confidential business activities and relationships, and state security. Communications are bounced around a distributed network of servers called onion routers, protecting you from websites that build profiles of your interests, local eavesdroppers that read your data or learn what sites you visit, and even the onion routers themselves.
Tor’s security is improved as its user base grows and as more people volunteer to run servers.
The Tor Browser Bundle lets you use Tor on Windows without needing to install any software. It can run off a USB flash drive, comes with a pre-configured web browser and is self contained. The Tor IM Browser Bundle additionally allows instant messaging and chat over Tor (Contains Tor, Vidalia, Torbutton, Polipo, Firefox, and Pidgin).
Tor runs on Windows 7, Vista, XP, 2000, 2003 Server, Mac OS X, Linux, BSD.