Author Topic: Tor is an anonymity online program that lets you defend against traffic analysis  (Read 2087 times)

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Tor is an anonymity online program that lets you defend against traffic analysis

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Tor: anonymity online

Tor is a software project that helps you defend against traffic analysis, a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security. Tor protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world: it prevents somebody watching your Internet connection from learning what sites you visit, and it prevents the sites you visit from learning your physical location. Tor works with many of your existing applications, including web browsers, instant messaging clients, remote login, and other applications based on the TCP protocol.

Hundreds of thousands of people around the world use Tor for a wide variety of reasons: journalists and bloggers, human rights workers, law enforcement officers, soldiers, corporations, citizens of repressive regimes, and just ordinary citizens.

There are three pieces of fine print you need to know about.

   1. Tor does not protect you if you do not use it correctly. Read our list of warnings and make sure to follow the instructions for your platform carefully.
   2. Even if you configure and use Tor correctly, there are still potential attacks that could compromise Tor's ability to protect you.
   3. No anonymity system is perfect these days, and Tor is no exception: you should not rely solely on the current Tor network if you really need strong anonymity.

Tor's security improves as its user base grows and as more people volunteer to run relays. (It isn't nearly as hard to set up as you might think, and can significantly enhance your own security against some attacks.) If running a relay isn't for you, we need help with many other aspects of the project, and we need funds to continue making the Tor network faster and easier to use while maintaining good security. Please donate.

Platform    
Windows
Vista, XP, 2000, 2003 Server, Millenium, 98SE    

Mac
Universal Binary (OSX 10.4 & 10.5)    

Mac
PowerPC Only (OSX 10.3)    

Linux/Unix packages
Redhat/CentOS, Fedora, Debian, Ubuntu, SUSE


Warning: Want Tor to really work?

...then please don't just install it and go on. You need to change some of your habits, and reconfigure your software! Tor by itself is NOT all you need to maintain your anonymity. There are several major pitfalls to watch out for:

   1. Tor only protects Internet applications that are configured to send their traffic through Tor — it doesn't magically anonymize all your traffic just because you install it. We recommend you use Firefox with the Torbutton extension.
   2. Browser plugins such as Java, Flash, ActiveX, RealPlayer, Quicktime, Adobe's PDF plugin, and others can be manipulated into revealing your IP address. You should probably uninstall your plugins (go to "about:plugins" to see what is installed), or investigate QuickJava, FlashBlock, and NoScript if you really need them. Consider removing extensions that look up more information about the websites you type in (like Google toolbar), as they may bypass Tor and/or broadcast sensitive information. Some people prefer using two browsers (one for Tor, one for unsafe browsing).
   3. Beware of cookies: if you ever browse without Tor and Privoxy and a site gives you a cookie, that cookie could identify you even when you start using Tor again. You should clear your cookies frequently. CookieCuller can help protect any cookies you do not want to lose.
   4. Tor anonymizes the origin of your traffic, and it encrypts everything inside the Tor network, but it can't encrypt your traffic between the Tor network and its final destination. If you are communicating sensitive information, you should use as much care as you would on the normal scary Internet — use HTTPS or other end-to-end encryption and authentication.
   5. While Tor blocks attackers on your local network from discovering or influencing your destination, it opens new risks: malicious or misconfigured Tor exit nodes can send you the wrong page, or even send you embedded Java applets disguised as domains you trust.


Be smart and learn more. Understand what Tor does and does not offer.



Tor: Overview

Tor is a network of virtual tunnels that allows people and groups to improve their privacy and security on the Internet. It also enables software developers to create new communication tools with built-in privacy features. Tor provides the foundation for a range of applications that allow organizations and individuals to share information over public networks without compromising their privacy.

Individuals use Tor to keep websites from tracking them and their family members, or to connect to news sites, instant messaging services, or the like when these are blocked by their local Internet providers. Tor's hidden services let users publish web sites and other services without needing to reveal the location of the site. Individuals also use Tor for socially sensitive communication: chat rooms and web forums for rape and abuse survivors, or people with illnesses.

Journalists use Tor to communicate more safely with whistleblowers and dissidents. Non-governmental organizations (NGOs) use Tor to allow their workers to connect to their home website while they're in a foreign country, without notifying everybody nearby that they're working with that organization.

Groups such as Indymedia recommend Tor for safeguarding their members' online privacy and security. Activist groups like the Electronic Frontier Foundation (EFF) recommend Tor as a mechanism for maintaining civil liberties online. Corporations use Tor as a safe way to conduct competitive analysis, and to protect sensitive procurement patterns from eavesdroppers. They also use it to replace traditional VPNs, which reveal the exact amount and timing of communication. Which locations have employees working late? Which locations have employees consulting job-hunting websites? Which research divisions are communicating with the company's patent lawyers?

A branch of the U.S. Navy uses Tor for open source intelligence gathering, and one of its teams used Tor while deployed in the Middle East recently. Law enforcement uses Tor for visiting or surveilling web sites without leaving government IP addresses in their web logs, and for security during sting operations.

The variety of people who use Tor is actually part of what makes it so secure. Tor hides you among the other users on the network, so the more populous and diverse the user base for Tor is, the more your anonymity will be protected.
Why we need Tor

Using Tor protects you against a common form of Internet surveillance known as "traffic analysis." Traffic analysis can be used to infer who is talking to whom over a public network. Knowing the source and destination of your Internet traffic allows others to track your behavior and interests. This can impact your checkbook if, for example, an e-commerce site uses price discrimination based on your country or institution of origin. It can even threaten your job and physical safety by revealing who and where you are. For example, if you're travelling abroad and you connect to your employer's computers to check or send mail, you can inadvertently reveal your national origin and professional affiliation to anyone observing the network, even if the connection is encrypted.

How does traffic analysis work? Internet data packets have two parts: a data payload and a header used for routing. The data payload is whatever is being sent, whether that's an email message, a web page, or an audio file. Even if you encrypt the data payload of your communications, traffic analysis still reveals a great deal about what you're doing and, possibly, what you're saying. That's because it focuses on the header, which discloses source, destination, size, timing, and so on.

A basic problem for the privacy minded is that the recipient of your communications can see that you sent it by looking at headers. So can authorized intermediaries like Internet service providers, and sometimes unauthorized intermediaries as well. A very simple form of traffic analysis might involve sitting somewhere between sender and recipient on the network, looking at headers.

But there are also more powerful kinds of traffic analysis. Some attackers spy on multiple parts of the Internet and use sophisticated statistical techniques to track the communications patterns of many different organizations and individuals. Encryption does not help against these attackers, since it only hides the content of Internet traffic, not the headers.
The solution: a distributed, anonymous network

Tor helps to reduce the risks of both simple and sophisticated traffic analysis by distributing your transactions over several places on the Internet, so no single point can link you to your destination. The idea is similar to using a twisty, hard-to-follow route in order to throw off somebody who is tailing you — and then periodically erasing your footprints. Instead of taking a direct route from source to destination, data packets on the Tor network take a random pathway through several relays that cover your tracks so no observer at any single point can tell where the data came from or where it's going.



To create a private network pathway with Tor, the user's software or client incrementally builds a circuit of encrypted connections through relays on the network. The circuit is extended one hop at a time, and each relay along the way knows only which relay gave it data and which relay it is giving data to. No individual relay ever knows the complete path that a data packet has taken. The client negotiates a separate set of encryption keys for each hop along the circuit to ensure that each hop can't trace these connections as they pass through.



Once a circuit has been established, many kinds of data can be exchanged and several different sorts of software applications can be deployed over the Tor network. Because each relay sees no more than one hop in the circuit, neither an eavesdropper nor a compromised relay can use traffic analysis to link the connection's source and destination. Tor only works for TCP streams and can be used by any application with SOCKS support.

For efficiency, the Tor software uses the same circuit for connections that happen within the same ten minutes or so. Later requests are given a new circuit, to keep people from linking your earlier actions to the new ones.



Hidden services

Tor also makes it possible for users to hide their locations while offering various kinds of services, such as web publishing or an instant messaging server. Using Tor "rendezvous points," other Tor users can connect to these hidden services, each without knowing the other's network identity. This hidden service functionality could allow Tor users to set up a website where people publish material without worrying about censorship. Nobody would be able to determine who was offering the site, and nobody who offered the site would know who was posting to it.
Staying anonymous

Tor can't solve all anonymity problems. It focuses only on protecting the transport of data. You need to use protocol-specific support software if you don't want the sites you visit to see your identifying information. For example, you can use web proxies such as Privoxy while web browsing to block cookies and withhold information about your browser type.

Also, to protect your anonymity, be smart. Don't provide your name or other revealing information in web forms. Be aware that, like all anonymizing networks that are fast enough for web browsing, Tor does not provide protection against end-to-end timing attacks: If your attacker can watch the traffic coming out of your computer, and also the traffic arriving at your chosen destination, he can use statistical analysis to discover that they are part of the same circuit.
The future of Tor

Providing a usable anonymizing network on the Internet today is an ongoing challenge. We want software that meets users' needs. We also want to keep the network up and running in a way that handles as many users as possible. Security and usability don't have to be at odds: As Tor's usability increases, it will attract more users, which will increase the possible sources and destinations of each communication, thus increasing security for everyone. We're making progress, but we need your help. Please consider running a relay or volunteering as a developer.

Ongoing trends in law, policy, and technology threaten anonymity as never before, undermining our ability to speak and read freely online. These trends also undermine national security and critical infrastructure by making communication among individuals, organizations, corporations, and governments more vulnerable to analysis. Each new user and relay provides additional diversity, enhancing Tor's ability to put control over your security and privacy back into your hands.

http://www.torproject.org/index.html.en

 

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