The following is a Security  Bulletin from the Microsoft Product Security
Notification Service.

Please do not  reply to this message,  as it was sent  from an unattended
mailbox.
                    ********************************

-----BEGIN PGP SIGNED MESSAGE-----

- --------------------------------------------------------------------
Title:      Malformed WebDAV Request Can Cause IIS
            to Exhaust CPU Resources
Released:   08 March 2001
Revised:    13 March 2001 (version 2.0)
Software:   IIS 5.0
Impact:     Denial of Service
Bulletin:   MS01-0016

Microsoft encourages customers to review the Security Bulletin at:
https://www.microsoft.com/technet/security/bulletin/MS01-016.asp
- --------------------------------------------------------------------

Reason for Revision:
====================
The original version of this bulletin provided a workaround
(discussed in Knowledge Base article Q241520) that would protect
affected systems by disabling WebDAV services. However, a security
patch is now available that eliminates the vulnerability, and
Microsoft recommends using the patch rather than the workaround. We
have updated both the bulletin and the narrative below to reflect
this.

Issue:
======
WebDAV is an extension to the HTTP protocol that allows remote
authoring and management of web content. In the Windows 2000
implementation of the protocol, IIS 5.0 performs initial processing
of all WebDAV requests, then forwards the appropriate commands to the
WebDAV process. However, a flaw exists in the way WebDAV handles a
particular type of malformed request. If a stream of such requests
were directed at an affected server, it would consume all CPU
availability on the server.

The patch should be applied to all machines running IIS 5.0. While
this obviously includes web servers, it's worth noting that IIS 5.0
may be running on other types of servers as well, particularly mail
servers running Exchange 2000.

Mitigating Factors:
====================
 - The effect of an attack via this vulnerability would be
   temporary. The server would automatically resume normal
   service as soon as the malformed requests stopped arriving.

 - The vulnerability does not provide an attacker with any
   capability to carry out WebDAV requests.

 - The vulnerability does not provide any capability to
   compromise data on the server or gain administrative
   control over it.

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin
   https://www.microsoft.com/technet/security/bulletin/ms01-016.asp
   for information on obtaining this patch.

- -------------------------------------------------------------------


-----BEGIN PGP SIGNATURE-----
Version: PGP Personal Privacy 6.5.3

iQEVAwUBOq7jso0ZSRQxA/UrAQF1QwgAlgv97QgEKhq/VR39SSQTzq4nEgvj0XFy
jWrxuIwFlOKiIVFV61Tjjip7HSex1OgZF4UD1EafPeNcNmE+A157Ufk3/QeQXzxO
dY0AF/cvSlGvBOk52Pw/RgYPbpez8/dAzgabz7vyDDm6zL1gqX7SKqNnzPEnldzy
8gB17X5KMduRdDSqTW7Rf09lFd9covzSZNGIDLnfzjBQiuA9UilgxxaDarfBrf67
lZ1oTjmdH1MRC39ki/p8ye0T5LSMT3AIRVCLFaJmqtOLoBV5bCIMpc1DtJhJJNqq
t3uCTi0fCcWLxLvGucix+/a0INxJtF2CZCxPoPkn6yHB92rwYBgQ4w==
=YUwQ
-----END PGP SIGNATURE-----

   *******************************************************************
You have received  this e-mail bulletin as a result  of your registration
to  the   Microsoft  Product  Security  Notification   Service.  You  may
unsubscribe from this e-mail notification  service at any time by sending
an  e-mail  to  MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM
The subject line and message body are not used in processing the request,
and can be anything you like.

To verify the digital signature on this bulletin, please download our PGP
key at https://www.microsoft.com/technet/security/notify.asp.

For  more  information on  the  Microsoft  Security Notification  Service
please  visit  https://www.microsoft.com/technet/security/notify.asp.  For
security-related information  about Microsoft products, please  visit the
Microsoft Security Advisor web site at https://www.microsoft.com/security.