Understanding the RUNAS Command in Windows 2000

This article examines the function, operation, and security benefits of the RUNAS command-line utility in Microsoft Windows 2000. It explains how administrators and standard users leverage this built-in tool to run specific programs using alternate security credentials without logging off, thereby supporting the security principle of least privilege.

The primary function of the runas command-line utility in Microsoft Windows 2000 is to allow an active user to execute programs, management consoles, and scripts under a different user account context than the currently logged-on session. Most commonly, it permits standard users to run administrative utilities by providing administrator credentials on demand.

The Principle of Least Privilege

Prior to Windows 2000, administrators routinely logged into workstations using administrative accounts to perform daily tasks, such as browsing the web or checking email. This exposed the entire operating system to compromise if malicious code executed under those elevated rights.

The RUNAS command addresses this vulnerability by enforcing the principle of least privilege. Under this model, administrators log in using standard, non-privileged user accounts for day-to-day operations. When an administrative task is required—such as modifying system files, managing user accounts, or installing software—the administrator uses RUNAS to spawn only that specific application with elevated permissions.

Underlying Mechanism: The Secondary Logon Service

The RUNAS utility relies on the Windows 2000 Secondary Logon service (seclogon). When invoked, RUNAS prompts the user for the target account's password, validates the credentials with the Local Security Authority (LSA), and creates a new process with an access token corresponding to the specified credentials rather than the interactive user's token. If the Secondary Logon service is disabled or stopped, the RUNAS command fails.

Syntax and Common Usage

The basic syntax for the command is:

runas /user:ComputerOrDomain\Username "program_name"

Common usage scenarios include:

• Launching the Microsoft Management Console:
  runas /user:Administrator "mmc %windir%\system32\compmgmt.msc"
• Opening an elevated Command Prompt:
  runas /user:DOMAIN\AdminUser "cmd.exe"
• Launching local device management:
  runas /user:LocalMachine\Administrator "control.exe"

The /netonly switch is also available to run an application locally under the current user context while using alternate credentials strictly for remote network access.

Limitations in Windows 2000

While RUNAS significantly enhances operational security, it contains specific limitations within Windows 2000:

• It cannot directly launch Windows Explorer (explorer.exe) in an elevated context because the operating system shares a single desktop process across the user session.
• It does not allow credentials or passwords to be piped or hardcoded in batch scripts; passwords must be entered interactively at the command prompt to prevent plaintext credential exposure.
• It operates on separate user profiles, meaning an application launched with RUNAS reads and writes registry keys and environment variables associated with the target account rather than the logged-on account.