windows account

you can check current login Enviorment.User in Active Directory via Directory Services

here is the code:

 DirectoryEntry adsEntry = new DirectoryEntry(path, strAccountId, strPassword);
DirectorySearcher adsSearcher = new DirectorySearcher( adsEntry );
//adsSearcher.Filter = "(&(objectClass=user)(objectCategory=person))";
adsSearcher.Filter = "(sAMAccountName=" + strAccountId + ")";

try 
 {
  SearchResult adsSearchResult = adsSearcher.FindOne();
  bSucceeded = true;

  strAuthenticatedBy = "Active Directory";
  strError = "User has been authenticated by Active Directory.";
  adsEntry.Close();
 }
catch ( Exception ex )
 {
  // Failed to authenticate. Most likely it is caused by unknown user
  // id or bad strPassword.
  strError = ex.Message;
  adsEntry.Close();
 }