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I'm new to cybersecurity, but I always knew some basic things, or at least I thought so, until I found out that the Flash app may actually get my real IP address even if I'm behind elite proxy. How does Flash find out the real IP? What is the technique for this and is it possible to secure myself from it without disabling Flash? How can I check if I am in fact vulnerable to this?

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It's because flash doesn't actually care for your proxy preferences. You can change that in your flash player settings, but even then, flash applications can choose to try to connect directly and ignore your proxy settings. A proxy is nothing more than a "suggestion" to a program. It is up to the programs to actually follow those settings, or ignore them. A webbrowser doing HTTP by itself will probably honor your proxy settings, but technologies outside, or "next to" the browser (like plugins and WebRTC) may simply do whatever it wants.

  • Could you please tell how can I troubleshoot it? I mean how can I know if some specific flash app request my IP identity or not? – afriendofafriend Dec 6 '16 at 22:16
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    You pretty much can't. At best you have two options: track ALL connections or use an application firewall to block all applications that are connecting outside of the proxy. I'm guessing you are on Windows as that's where most novice proxy users are, in which case TCPView (sysinternals/microsoft) might be a place to start. Netstat is another tool, but might be hard to use if you are not familiar with cli tools. – John Keates Dec 6 '16 at 22:30
  • In most corporate environments, in order to enforce the use of a proxy, the perimeter firewall will restrict traffic to that originating from, or returning to, the proxy so if your software doesn't respect the proxy settings it won't get access to the internet. Many home routers will also allow you to restrict traffic to your proxy and if you want to enforce proxy use then this is a good thing to do (although some software that decides to ignore the proxy may 'break'). – David Scholefield Dec 7 '16 at 7:43
  • Depends on the proxy, if it is a basic HTTP proxy that would break pretty much everything. – John Keates Dec 7 '16 at 18:05

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