How can you "print" a specific computer behind a firewall using HttpContext?

Question

I need to be able to identify one system from another in ASP.Net using everything that is available in HttpContext. I tried to use many available ServerVariables, but often systems are configured from an image-based disk. So, due to the firewall, their IP address is the same, and all of their ServerVariables (browseragent, logonuser) are the same, I need to find something else that will distinguish different machines. Since the site is protected by authentication forms, Windows Integrated Authentication must be disabled (otherwise I will have access to various Logon_User values).

I am not married to HttpContext, but it seems to me that the only way to use the code is to obtain identifiable user information.

EDIT / UPDATE:

@ Robert Harvey provided a couple of links that yielded a lot of results, most of which didn’t match my score for one reason or another (although there are some more great ideas that I didn’t know in, I thought before). First of all, I need to determine if someone switched the machines behind the firewall. Therefore, I will provide some details of the code structure that shed light on why some things do not work for me.

• Sessions / Cookies are permanent until midnight (the decision is made over my head, I live with it)
• The authenticated user does not use the MembershipUser Class. (even if it did, MemberhipUser.IsOnline offer me nothing but a previously registered user)
• Users know to delete cookies or close browsers without logging out.
• I need some criteria that a machine can from another, not necessarily to prevent simultaneous logon, but to identify them.

Answer 1

This is an answering machine. I came across Browser Spy , and although it does not take into account the specifics of how to do this, it shows that this is possible by combining these elements to uniquely identify a specific system with a minimum margin of error.

Answer 2

cookie .

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