Microsoft KB Archive/236359

= Denial of Service Attack Using Unprotected IOCTL Function Call =

Article ID: 236359

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition

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This article was previously published under Q236359



SYMPTOMS
When you run a program on a computer running Windows NT that contains an Input Output Control (IOCTL) function call for the mouse or keyboard, the program may prevent those input devices from responding to the operating system. A program that improperly uses an Windows NT IOCTL function call may be employed to create a denial of service attack on the computer by disabling the mouse and keyboard.



CAUSE
This problem occurs because the IOCTLs for the mouse and keyboard are unprotected and are available for use by all users, regardless of their security privileges. Restarting the computer can correct the situation, but does not prevent the program from being run again.

NOTE: This vulnerability does not allow any data to be compromised, nor does it provide a way to bypass security and allow a user to elevate their security privileges.



Windows NT Server or Workstation 4.0
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:


 * http://www.microsoft.com/windows/servicepacks/ -or-


 * 152734 how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/directory/overview.asp

Windows NT Server 4.0, Terminal Server Edition
To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack



WORKAROUND
To work around this problem, follow normal recommended security practices to prevent kiosk-type workstations from running unapproved programs. Servers should generally allow only administrators to log on interactively and run programs.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows NT Server version 4.0, Terminal Server Edition Service Pack 6. This problem was first corrected in Windows NT Server 4.0, Terminal Server Edition, Service Pack 5.



MORE INFORMATION
Windows NT provides the ability for programs to directly request services of device drivers. The interface through which this is done is called an Input Output Control (IOCTL). Like all operating system services, some IOCTLs are appropriate for normal users to use and others are reserved for privileged users.

For computers running Windows NT Workstation or Windows NT Server, this attack prevents the mouse and keyboard from returning to service when a user logs off. For example, if a kiosk workstation allows users to run a program arbitrarily, or if a server allowed normal users to log on interactively and run a program arbitrarily, a malicious user could disable the computer's keyboard and mouse and prevent use of the computers until it had been restarted. For Windows NT Server 4.0, Terminal Server Edition, this exploit disables not only the keyboard and mouse on the local computer, but also those on the console. This would not interfere with any of the ongoing terminal server sessions, but would still require the computer to be restarted to gain control of the console.

For additional security-related information about Microsoft products, please visit the following Microsoft Web site:

http://www.microsoft.com/security/

Additional query words: MS99-024

Keywords: kbhotfixserver kbqfe kbbug kbfile kbfix kbinterop kbprogramming kbqfe KB236359

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