GetAdmin Utility Grants Users Administrative Rights

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

A utility, Getadmin.exe, is being circulated on the Internet that grants normal users administrative rights by adding them to the Administrators group. This utility can be run from any user context except Guest and grants a local user account administrative rights.

This problem does not occur on Windows NT 3.51.

CAUSE

Getadmin.exe works because of a problem in a low-level kernel routine that causes a global flag to be set which allows calls to NtOpenProcessToken to succeed regardless of the current users permissions. This in turn allows a user to attach to any process running on the system, including a process running in the system's security context, such as WinLogon. Once attached to such a process, a thread can be started in the security context of the process.

In the specific case of GetAdmin, it attaches to the WinLogon process, which is running in the system's security context, and makes standard API calls that add the specified user to the administrators group.

It is important to note that any account which has been granted the rights to "Debug Programs" will always be able to run Getadmin.exe successfully, even after the application of the hotfix. This is because the "Debug Programs" right allows a user to attach to any process. The "Debug Programs" right is initially granted to Administrators and should be only granted to fully trusted users.

Also, if Getadmin.exe is run with an account that is already a member of the administrators local group, it will still work (even after applying the hotfix). This is by design. Members of the administrators group always have the rights to make the calls GetAdmin needs in order to succeed.

RESOLUTION

A fix to the Windows NT Kernel routine which was being used to set the global flag has been developed by Microsoft. This fix prevents an application, such as Getadmin.exe, from attaching to WinLogon (or any other process not owned by the user) and from granting administrative rights to users.

To resolve this problem, obtain the hotfix below, or wait for the next service pack.

This hotfix has been posted to the following Internet location:

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt40/
   hotfixes-postSP3/getadmin-fix

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

MORE INFORMATION

Getadmin.exe must be executed locally and works for accounts on a workstation or member server and for domain accounts on a primary domain controller (PDC). The utility does not function on a backup domain controller (BDC) because the account database on a BDC is read only. The only way to use GetAdmin to modify a domain account database is to log on to a primary domain controller and run the utility locally on the PDC.

For more information on Windows NT security, please see the following Internet sites:

• http://www.microsoft.com/security/
• http://www.microsoft.com/ntserver/guide/securityupdate.asp

   http://www.microsoft.com/