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How to spoof the OS?

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cujoc
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Post Posted January 17th, 2008, 6:25 am

Is there a way to spoof the Operating System in Firefox? I am on a Linux machine, and would like to know if there is a way to spoof the OS, so that a website I visit will think I am on a Windows system?

I know that I can spoof the Useragent. But if I have Javascript enabled, my real Operating System can still be found out even with a spoofed useragent (on sites like http://www.showmyip.com/?version=full , it is shown at CPU class/type and Operating System Platform).

How does Javascript find out this information? Can a website also find out the real OS by other means, for example by looking at the way how the browser behaves or how it handles plugins?

Thanks for your help.

teoli2003
 
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Joined: November 10th, 2005, 2:54 am

Post Posted January 17th, 2008, 6:36 am

It is not javascript that find this information, but the server. There is some possibility to discover the OS you are using by analysing TCP packets. This can be done in a passive way or an active way (more precisely but detectable).

To fake this, you have to use a specifically crafted TCP stack, though maybe some firewall can fake this.

cujoc
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Post Posted January 17th, 2008, 7:21 am

Thanks. But if I go to http://www.showmyip.com/?version=full without Javascript enabled and with a spoofed useragent (which fakes the Operating System), the website does not detect my real OS. The website only detects my real useragent if I have Javascript enabled.

In this case, it seems that it is Javascript which gives away the real OS.

I know that the website could probably also find out the real OS by analysing TCP packets or by how the browser handles plugins, and this would be more difficult or impossible to spoof.

cujoc
Guest
 

Post Posted January 17th, 2008, 7:25 am

Correction:

The website only detects my real useragent if I have Javascript enabled.

should read:

The website only detects my real <b>OS</b> if I have Javascript enabled.

VanillaMozilla
 
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Joined: November 7th, 2005, 11:26 am

Post Posted January 17th, 2008, 7:52 am

I think you have it figured out.

You could try running under Wine.

dickvl

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Post Posted January 17th, 2008, 5:25 pm

<a href="data:text/html;base64,PGh0bWw+PGJvZHk+PHNjcmlwdD52YXIgaW5mbz0nQnJvd3NlciBJbmZvcm1hdGlvbjo8YnI+JzsgZm9yKHZhciBwcm9wIGluIG5hdmlnYXRvcil7aWYodHlwZW9mIG5hdmlnYXRvcltwcm9wXSAhPSAnZnVuY3Rpb24nICYmIHR5cGVvZiBuYXZpZ2F0b3JbcHJvcF0gIT0gJ29iamVjdCcpIGluZm8rPXByb3ArJzogJytuYXZpZ2F0b3JbcHJvcF0rJzxicj4nfTtkb2N1bWVudC5vcGVuKCk7ZG9jdW1lbnQud3JpdGUoaW5mbyk7ZG9jdW1lbnQuY2xvc2UoKTs8L3NjcmlwdD48L2JvZHk+PC9odG1sPg==">Browser Info</a>

Anonymosity
 
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Joined: May 7th, 2007, 12:07 pm

Post Posted January 17th, 2008, 6:05 pm

If you can filter the web page content with a local proxy like Proxomitron, you can use Javascript but disable the code that can detect the real user-agent. By getting rid of the codes "function getObjects", "function getElement", "navigator.userAgent", "navigator.appName", and "navigator.appVersion" (or substituting nonsense for those strings), you disable the ability to detect the real information.

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