Security Advisory

Microsoft Security Advisory 956187

Increased Threat for DNS Spoofing Vulnerability

Published: July 25, 2008

Microsoft released Microsoft Security Bulletin MS08-037 on July 8, 2008, offering security updates to protect customers against Windows Domain Name System (DNS) spoofing attacks. Microsoft released this update in coordination with other DNS vendors who were also similarly impacted. Since the coordinated release of these updates, the threat to DNS systems has increased due to a greater public understanding of the attacks, as well as detailed exploit code being published on the Internet.

Microsoft is not currently aware of active attacks utilizing this exploit code or of customer impact at this time. However, attacks are likely imminent due to the publicly posted proof of concept and Microsoft is actively monitoring this situation to keep customers informed and to provide customer guidance as necessary.

Microsoft’s investigation of this exploit code has verified that it does not affect Microsoft customers who have installed the updates detailed in Microsoft Security Bulletin MS08-037. Microsoft continues to recommend that customers apply the updates to the affected products by enabling the Automatic Updates feature in Windows.

Microsoft has identified known issues with the updates offered in Microsoft Security Bulletin MS08-037. For more information about known installation issues, see Frequently Asked Questions (FAQ) Related to This Security Update in Microsoft Security Bulletin MS08-037, and Known issues with this security update in Microsoft Knowledge Base Article 953230.

General Information

Overview

Purpose of Advisory: To inform customers of the increased threat and to recommend that customers install the updates offered in Microsoft Security Bulletin MS08-037 immediately.

Advisory Status: Advisory published. As this issue is already addressed as part of Microsoft Security Bulletin MS08-037, no additional update is required.

Recommendation: Review the referenced bulletin and apply the appropriate update for increased security.

This advisory discusses the following software.

Frequently Asked Questions

What is the scope of the advisory?
The scope of the advisory is to notify customers of the increased threat to Microsoft DNS implementations and to recommend that customers install the update from Microsoft Security Bulletin MS08-037 immediately.

Is this a security vulnerability that requires Microsoft to issue a security update?
No. Customers who have installed the updates offered by Microsoft Security Bulletin MS08-037 are not affected by this vulnerability.

What causes this threat?
The Windows DNS service in the Windows DNS client and DNS server does not provide enough entropy when performing DNS queries.

What is the Domain Name System (DNS)?
Domain Name System (DNS) is one of the industry-standard suite of protocols that comprise TCP/IP. DNS is implemented using two software components: the DNS server and the DNS client (or resolver). Both components are run as background service applications. Network resources are identified by numeric IP addresses, but these IP addresses are difficult for network users to remember. The DNS database contains records that map user-friendly alphanumeric names for network resources, such as www.microsoft.com, to the IP addresses used by those resources for communication. In this way, DNS acts as a mnemonic device, making network resources easier to remember for network users. For more information and to view logical diagrams illustrating how DNS fits with other Windows technologies, review the TechNet article What Is DNS?

What is DNS cache?
Domain Name System (DNS) caching resolver service, or “DNS cache,” is a service that saves the responses to DNS queries so that the DNS server is not repeatedly queried for the same information. For more information, see the TechNet article, DnsCache, or the TechNet article, DNS Resolver Cache Service. See the TechNet article, Attack detection, for more information on DNS cache poisoning.

What might an attacker use this function to do?
An attacker who has successfully exploited this vulnerability can insert arbitrary addresses into the DNS cache, also known as DNS cache poisoning.

Suggested Actions

• Microsoft recommends that customers install the updates offered in Microsoft Security Bulletin MS08-037 immediately.

Other Information

Resources:

• You can provide feedback by completing the form by visiting Microsoft Help and Support: Contact Us.
• Customers in the United States and Canada can receive technical support from Microsoft Product Support Services. For more information about available support options, see Microsoft Help and Support.
• International customers can receive support from their local Microsoft subsidiaries. For more information about how to contact Microsoft for international support issues, visit International Support.
• Microsoft TechNet Security provides additional information about security in Microsoft products.

Disclaimer:

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions:

• July 25, 2008: Advisory published.

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