Use privoxy and Tor for increased anonymity

Introduction

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 (from https://www.torproject.org/).

There are Tor Bundles that you can install but you can also chain Tor through a proxy.

I’ll use an Ubuntu 1214 vmware machine to proxy my traffic. The VM has one shared network interface.

Privoxy

Privoxy is a non-caching web proxy. It has some filtering capabilities but for this setup I’ll only use the proxying capabilities.

Installing privoxy on Ubuntu is straightforward

apt-get install privoxy

The configuration of privoxy is done in /etc/privoxy/config. On a VM setup you can configure privoxy to listen on the public interface

listen-address  0.0.0.0:8118

To increase anonymity you should disable logging by commenting this line

# logfile logfile

Then set privoxy to chain the traffic to Tor

forward-socks5   /               127.0.0.1:9050 .

Tor

Now we’ll have to install Tor. There’s an Ubuntu package for Tor.

apt-get install tor

That’s all there is for getting Tor started.

By default, the Tor proxy is set to server type 4. If you want to use it chained with privoxy you have to switch to type 5.

server_type = 5

Setting the proxy in a browser

Most browsers can be configured to use a proxy. Changing the configuration can be a pain if you want to switch often between using the Tor proxy or not. Firefox has a plugin that can take care of this switching and it is called Proxy Selector.

After installing the plugin you can add your new proxy. By default privoxy runs on tcp/8118.

Testing

Start both services.

/etc/init.d/tor restart
/etc/init.d/privoxy restart

Make sure the proxy settings are correct and now point your browser to http://config.privoxy.org/show-status. Privoxy will intercept this request and show you its configuration settings.

Now you’ll have to check that your newly configured browser is using Tor. With the proxy disabled (or via another browser that is not using the proxy) go to the website http://whatismyipaddress.com/. Note the IP. Then enable the proxy and visit that website again. It should list another IP. Do the same for SSL enabled websites (https) via https://ipdb.at/.

Other applications

Tor can act as a SOCKS proxy for other applications. Open the configuration file /etc/torsocks.conf and search for the option server_type to set the SOCKS proxy type.

Legal issues

The legal framework and why (or why not) you should use Tor is described in detail on the Tor Exit Router information page of UCL.

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