Article ID: 816118 - View products that this article applies to.
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/256986/EN-US/ )Description of the Microsoft Windows Registry
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SUMMARYThis step-by-step article describes how to configure the remote access client account lockout feature. Remote access clients include direct dial-in and virtual private network (VPN) clients.
You can use the remote access account lockout feature to specify how many times a remote access authentication has to fail against a valid user account before the user is denied access. An attacker can try to access an organization through remote access by sending credentials (valid user name, guessed password) during the VPN connection authentication process. During a dictionary attack, the attacker sends hundreds or thousands of credentials by using a list of passwords based on common words or phrases.
The advantage of activating account lockout is that brute force attacks, such as a dictionary attack, are unlikely to be successful because statistically at least, the account is locked out long before a randomly issued password is likely to be correct. Note that an attacker can still create a denial of service condition that intentionally locks out user accounts.
Configure Remote Access Client Account Lockout FeatureThe remote access account lockout feature is managed separately from the account lockout settings that are maintained in Active Directory Users and Computers. Remote access lockout settings are controlled by manually editing the registry. Note that these settings do not distinguish between a legitimate user who mistypes a password and an attacker that is trying to "crack" an account.
Remote access server administrators control two features of remote access lockout:
Activate Remote Access Client Account LockoutWARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
The failed attempts counter is periodically reset to zero (0). If an account is locked out after the maximum number of failed attempts, the failed attempts counter is automatically reset to zero after the reset time. To activate remote access client account lockout and reset time, follow these steps:
Manually Unlock a Remote Access ClientIf the account is locked out, the user can try to log on again after the lockout timer has run out, or you can delete the DomainName:UserName value in the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RemoteAccess\Parameters\AccountLockoutregistry key. To manually unlock an account, follow these steps:
REFERENCESFor additional information about the remote access client lockout feature, search Microsoft Windows Server 2003 Help and Support for "remote access account lockout".
Article ID: 816118 - Last Review: December 3, 2007 - Revision: 5.4