Firefox 3.5 DNS leaks

Discussion in 'Keeping Your Anonymity In Iran' started by Unregistered, Nov 1, 2009.

  1. Upgrading to FF3.5 may lead to DNS leaks when you are using secure proxies, even if it didn't leak before.

    DNS leaks are irrelevant to the websites you visited. But you ISP's DNS server will know the URL's you want to visit.

    The details. FF3.5 made some internal changes regarding the timing of the DNS requests and the http requests. They are themselves not bugs. If you enter your proxy into FF manually, and set network.proxy.socks_remote_dns to True, there will not be leaks.

    Proxy switching add-ons such as Foxy Proxy, switch proxy at every http request, and try to preserve the default proxy of your browser in between switches. DNS leaks occur because the requests are not synchronized with the http requests, selecting the wrong proxy for DNS. There may be options in Foxy to correct this with sock proxies. But fast and popular secure proxies like Ultrasurf isn't a sock proxy.

    The safer way to avoid leaks is to use a simple proxy switch add-on like Multiproxy Switch. The selected proxy is the proxy in use at all times.
  2. DNS leak test

    Download and run free Wireshark

    Start capture with the first icon.

    Pick the active network interface card.

    Select options.

    Set the capture filter to "port 53".

    If you capture any DNS packets that means there are leaks. However, ultrasurf occasionally send mysterious to get server information or to fool blockers. The DNS requests are not the websites you are visiting, but maybe harmless sites google and yahoo.
  3. ericjung Member

    Fixed in FoxyProxy 2.16


    This is fixed in FoxyProxy Standard 2.16, FoxyProxy Basic 1.3, and FoxyProxy Plus 3.3. Try it with Wireshark to see for yourself.

    Best regards,
    Eric Jung
  4. Just read this thread now. Thanks for sorting this so quickly Eric. :)

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