What default credential Directory Entry binds to if it is running as a service on Windows

If I bind to a DirectoryEntry ( without any arguments) on the application mode to search all the users at my current domain, I could see the logged in in user is the default credential for DirectoryEntry since it finds all the users for my domain. With that, I would expect that this won't work if the application is run at service mode since account for service is SYSTEM which is not a user of my domain. However the code still works and it could get all the users of m开发者_运维知识库y logged in user domain.

I did some search on internet, I didn't find any answer on this when running as a service. Any idea? Any way I could get that default credential at power shell?

---

At service mode, the default credential for directory entry would be the credential which computer is used to login into the domain (called computer login). See this link: https://serverfault.com/questions/61191/what-happens-when-a-computer-joins-an-active-directory-domain.

I first tried to use System.Net.CredentialCache::DefaultNetworkCredentials to try to get the default credential, however I found out the user and domain are all blank. It is confirmed from MSDN that we could not view those info with the returned NetworkCredentials.

So I added the following vb script (got the base code from this link: http://blogs.technet.com/b/heyscriptingguy/archive/2008/05/12/how-can-i-determine-the-distinguished-name-of-the-ou-where-the-logged-on-user-s-user-account-resides.aspx) to be called from power shell to get the dn of the current user and save it to a file.

Set objSysInfo = CreateObject("ADSystemInfo")
strUserName = objSysInfo.UserName
Set objUser = GetObject("LDAP://" & strUserName)
Wscript.Echo objUser.distinguishedName
Set objFS = CreateObject("Scripting.FileSystemObject")
strTemp = "c:\temp\dn.txt"
Set objOutFile = objFS.CreateTextFile(strTemp,True)    
objOutFile.Write(objUser.distinguishedName)
objOutFile.Close

Then when I ran it in service context, I found out that user is my computer itself, like this:

CN=my computer name,OU=Domain computer accounts,DC=domain,DC=local