The Privacy BlogPrivacy, Security, Cryptography, and Anonymity

Jan/15

5

Are free proxies hurting your security?

Looking in Dark Box

I have long said that privacy services are all about trust. I this article demonstrating how to use a simple web proxy to compromise the users of that proxy. Of course, the operator of the proxy is being untrustworthy, but that is the whole point. If you don’t have a reason to specifically trust the operator of your privacy service, you need to assume that they are attempting to do you harm. Of course, the same argument applies to Tor. Literally anyone could be running that proxy for any purpose.

Why are free proxies free?

I recently stumbled across a presentation of Chema Alonso from the Defcon 20 Conference where he was talking about how he created a Javascript botnet from scratch and how he used it to find scammers and hackers.

Everything is done via a stock SQUID proxy with small config changes.

The idea is pretty simple:

  1. [Server] Install Squid on a linux server
  2. [Payload] Modify the server so all transmitted javascript files will get one extra piece of code that does things like send all data entered in forms to your server
  3. [Cache] Set the caching time of the modified .js files as high as possible

Read the whole article.

Lance Cottrell is the Founder and Chief Scientist of Anonymizer. Follow me on Facebook, Twitter, and Google+.

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1 comment

  • Lauren · March 12, 2015 at 2:52 pm

    Great post about using free proxies. It is important to know the security danger. Thanks for sharing!

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