Microsoft Security Advisory (954157)

What is the scope of the advisory? 
This advisory provides notification that a defense-in-depth update described in this advisory is available through automatic updating and is also described in Microsoft Knowledge Base Article 954157. This update affects the software listed in the Affected Software table.

What is the Indeo Codec?
The Indeo Codec is a codec that decompresses digital media files for use in applications like Windows Media Player. For more information on codecs, see Using codecs.

How could an attacker exploit the vulnerability? 
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the Web site. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site.

It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

Another way that an attacker could exploit this vulnerability is to get specially crafted media content onto a user's system that leverages the Indeo codec.

Is there a change in user experience after this update is installed? 
After the updates discussed in this article are installed, users may notice that media content from Web sites may no longer be loaded in Internet Explorer or in Windows Media Player. Applications or games that use this codec from content located on the local system will continue to work.

How do I disable the Indeo codec? 
It is possible to disable this codec by deregistering the codec. Deregistering the codec will prevent any application or media content from using this codec. For directions on how to deregister the codec, see Microsoft Knowledge Base Article 954157.

How do I re-enable the use of this codec after this update is installed? 
It is possible to re-enable the functionality of the Indeo codec after this update is installed. Re-enabling the codec will expose users to the risk of a remote code execution attack and should only be considered if the need for the functionality of the codec outweighs the risk of exposure. For more information on how to re-enable the codec functionality, see Microsoft Knowledge Base Article 954157.

Why are there two parts to the update associated with this advisory? 
There are two parts to this update that help mitigate the risks associated with the Indeo codec. One is the update to Quartz.dll, which is the primary binary used by Windows Media Player. The second is the update that is provided by Application Compatibility Shim technology. The Media player update prevents applications from opening media content that leverages the Indeo codec from playing in the Internet zone, while the Application Compatibility Shim technology update stops Internet Explorer and Windows Media Player from loading media content that uses the Indeo codec.

Why is this update not associated with a Security Bulletin? 
This update is not associated with a security bulletin because it does not remediate specific vulnerabilities, but instead provides additional defense-in-depth mitigations to bring older operating systems closer to the same level of security protection as Windows Vista and Windows 7. Customers should apply this update to mitigate the threat in common scenarios, and evaluate deregistering the Indeo codec to remove access to the codec in any scenario.

Why is Microsoft not fixing specific vulnerabilities in this update? 
The Indeo codec is an older codec that is known to have several security vulnerabilities. Instead of fixing specific vulnerabilities, Microsoft is creating defense-in-depth changes that reduce the attack surface all together for known vulnerabilities, and future similar vulnerabilities.

Microsoft has not identified any mitigating factors for this vulnerability.

Workaround refers to a setting or configuration change that does not correct the underlying vulnerabilities but would help block known attack vectors. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

• Deregister the Indeo codec

  It is possible to disable this codec by deregistering the codec. For directions on how to deregister the codec, see Microsoft Knowledge Base Article 954157.

  Impact of workaround. Deregistering the Indeo codec will prevent any application or media content from using this codec.

  How to undo the workaround. See Microsoft Knowledge Base Article 954157 for information on how to undo this workaround.

• Review the Microsoft Knowledge Base Article that is associated with this advisory

  For more information about this issue, see Microsoft Knowledge Base Article 954157.

• Keep Windows Updated

  All Windows users should apply the latest Microsoft security updates to help make sure that their computers are as protected as possible. If you are not sure whether your software is up to date, visit Windows Update, scan your computer for available updates, and install any high-priority updates that are offered to you. If you have Automatic Updates enabled, the updates are delivered to you when they are released, but you have to make sure you install them. For more information about security updates, visit Microsoft Security Central.