By default, even with a correctly configured SOCKS proxy set up in firefox there will be DNS information leakage when firefox looks up domain names.

To force domain names to be resolved remotely, avoiding this information leakage do the following:

• Go to the Firefox address bar and type in about:config and hit enter
• Press "I'll be careful, I promise!" to dismiss the warning about changing settings

  

• network.proxy.socks" to narrow down the available options
• Double Click "network.proxy.socks_remote_dns" to change its value to "true"

  

  Changes take effect immediately and you can now close the tab, secure in the knowledge that your DNS requests are not bypassing the SSH tunnel