This article was previously published under Q313450
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A Simple Mail Transport Protocol (SMTP) service is installed by default in the Windows 2000 Server family of products. Exchange 2000, which you can install only on Windows 2000, uses the included Windows 2000 SMTP service instead of providing its own service. Windows 2000 Professional and Windows XP Professional include an SMTP service that is not installed by default. All of these implementations contain a flaw that could allow denial-of-service attacks to be mounted against the service.
The flaw involves the manner in which the service handles a particular type of SMTP command that is used to transfer the data that constitutes an incoming e-mail message. By sending a malformed version of this command, an attacker could stop the SMTP service or severely affect the performance of the SMTP service. This could disrupt mail services on the affected computer, but would not cause the operating system itself to stop working.
Microsoft Windows XP Home Edition does not include an SMTP service, and is not affected by the vulnerability.
Windows 2000 Professional and Windows XP Professional do provide an SMTP service, but it is not installed by default.
The Windows 2000 Server family of products install the SMTP service by default. However, best practices recommend that you disable any unnecessary services. Computers on which you have disabled the SMTP service are not at risk.
Microsoft Exchange 5.5 is not affected by the vulnerability, even if it is installed on a Windows 2000-based server.
The result of an attack would be limited to disrupting the SMTP service and, depending on the server's configuration, also possibly disrupting Microsoft Internet Information Services (IIS) and other Internet services. However, it would not disrupt any other server functions.
The vulnerability would not enable an attacker to gain any privileges on the affected server, or to access users' e-mail or data.
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.The English version of this fix should have the following file attributes or later:
Date Time Version Size File name ----------------------------------------------------- 06-Feb-2002 17:57 6.0.2600.28 431,104 Smtpsvc.dll
Windows XP Professional
Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft Windows XP Professional. This problem was first corrected in Windows XP Service Pack 1.
For more information about this vulnerability, visit the following Microsoft Web site: