According to this forum on [`WindowsIdentity.GetCurrent().Name` vs. `User.Identity.Name`][1]:

> * `User.Identity.Name` represents the identity passed from IIS.
> * `WindowsIdentity.GetCurrent().Name` is the identity under which the thread is running.


Depending on your app's authentication settings in IIS, they will return different values:



<pre><code><b>| <a href="https://msdn.microsoft.com/en-us/library/xh507fc5.aspx">Anonymous</a> | <a href="https://msdn.microsoft.com/en-us/library/aa292114.aspx">Impersonate</a> | User.Identity.Name | WindowsIndentiy.GetCurrent()  |</b>
|-----------|-------------|--------------------|-------------------------------|
| Yes       | True        | Empty String       | IUSR_&lt;<i>machineName</i>&gt;            |
| Yes       | False       | Empty String       | NT Authority\Network Service  |
| No        | True        | domain\user        | domain\user                   |
| No        | False       | domain\user        | NT Authority\Network Service  |
</code></pre>

**Legend**:

* Where **domain\user** will show up as:
  * domain\user for Active Directory
  * machineName\userName for local account
* Where **NT Authority\Network Service** will show up as:
 * NT Authority\Network Service for Windows Server or ASP.NET
 * machineName\ASPNET_WP for Windows XP

[1]: http://forums.asp.net/t/1507047.aspx

What's the difference in an asp.NET environment with Windows Authentication and Identity Impersonation turned on, between HttpContext.Current.User.Principal and WindowsIdentity.GetCurrent()?