Tor is a system intended to enable online anonymity, composed of client software and a network of servers which can hide information about users' locations and other factors which might identify them. Imagine a message being wrapped in several layers of protection: every server needs to take off one layer, thereby immediately deleting the sender information of the previous server.
Use of this system makes it more difficult to trace internet traffic to the user, including visits to Web sites, online posts, instant messages, and other communication forms. It is intended to protect users' personal freedom, privacy, and ability to conduct confidential business, by keeping their internet activities from being monitored. The software is open-source and the network is free of charge to use.
Like all current low latency anonymity networks, Tor cannot and does not attempt to protect against monitoring of traffic at the boundaries of the Tor network, i.e., the traffic entering and exiting the network. While Tor does provide protection against traffic analysis, it cannot prevent traffic confirmation (also called end-to-end correlation)
Caution: As Tor does not, and by design cannot, encrypt the traffic between an exit node and the target server, any exit node is in a position to capture any traffic passing through it which does not use end-to-end encryption such as TLS. (If your postman is corrupt he might still open the envelope and read the content). While this may or may not inherently violate the anonymity of the source, if users mistake Tor's anonymity for end-to-end encryption they may be subject to additional risk of data interception by third parties. So: the location of the user remains hidden; however, in some cases content is vulnerable for analysis through which also information about the user may be gained.
The Tor Browser Bundle lets you use Tor on Windows, OSX and/or Linux without requiring you to configure a Web browser. Even better, it's also a portable application that can be run from a USB flash drive, allowing you to carry it to any PC without installing it on each computer's hard drive.
You can download the Tor Browser Bundle from the torproject.org Web site (https://www.torproject.org), either as a single file (13MB) or a split version that is multiple files of 1.4 MB each which may proof easier to download on slow connections.
If the torproject.org Web site is filtered from where you are, type "tor mirrors" in your favorite Web search engine: The results probably include some alternative addresses to download the Tor Browser Bundle.
Caution: When you download Tor Bundle (plain or split versions), you should check the signatures of the files, especially if you are downloading the files from a mirror site. This step ensures that the files have not been tampered with. To learn more about signature files and how to check them, read https://wiki.torproject.org/noreply/TheOnionRouter/VerifyingSignatures
(You can also download the GnuPG software that you will need to check the signature here: http://www.gnupg.org/download/index.en.html#auto-ref-2)
The instructions below refer to installing Tor Browser on Microsoft Windows. If you are using a different operating system, refer to the torproject.org website for download links and instructions.
Note: You can choose to extract the files directly onto a USB key or memory stick if you want to use Tor Browser on different computers (for instance on public computers in Internet cafs).
Before you start:
Launch Tor Browser:
When a connection is established, Firefox automatically connects to the TorCheck page and then confirms if you are connected to the Tor network. This may take some time, depending on the quality of your Internet connection.
If you are connected to the Tor network, a green onion icon appears in the System Tray on the lower-right-hand corner of your screen:
Try viewing a few Web sites, and see whether they display. The sites are likely to load more slowly than usual because your connection is being routed through several relays.
If the onion in the Vidalia Control Panel never turns green or if Firefox opened, but displayed a page saying "Sorry. You are not using Tor", as in the image below, then you are not using Tor.
If you see this message, close Firefox and Tor Browser and then repeat the steps above. You can perform this check to ensure that you are using tor, at any time by clicking the bookmark button labelled "TorCheck at Xenobite..." in the Firefox toolbar.
If Firefox browser does not launch, another instance of the browser may be interfering with Tor Browser. To fix this:
There are two other projects that bundle Tor and a browser: