Microsoft Security Bulletin MS08-029 - Moderate

Microsoft has not identified any mitigating factors for this vulnerability.

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

• Microsoft Forefront Security for Exchange Server, Microsoft Forefront Security for SharePoint, and Microsoft Antigen support multiple engines in addition to the Microsoft Malware Protection Engine on a single system. If multiple engines are available on an affected system, administrators can disable the Microsoft Malware Protection Engine as a workaround, until the Microsoft Malware Protection Engine can be updated. Before disabling the Microsoft Malware Protection Engine, administrators should ensure they have installed the latest virus signatures for any third-party engine.
• We have not identified any workarounds for Windows Live OneCare, Microsoft Windows Defender and Microsoft Forefront Client Security.

What is the scope of the vulnerability? 
A denial of service vulnerability exists in the way that the Microsoft Malware Protection Engine parses files. An attacker could exploit the vulnerability by constructing a specially crafted file that could allow denial of service when received by the target computer system and scanned by the Microsoft Malware Protection Engine.

What causes the vulnerability? 
The Microsoft Malware Protection Engine does not properly validate input when parsing specially crafted files.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could make the Microsoft Malware Protection Engine non-responsive and restart.

How could an attacker exploit the vulnerability? 
An attacker could try to exploit the vulnerability by creating a specially crafted file and forcing an affected system to process the file. When Microsoft Malware Protection Engine on the target machine automatically scans the file, the file could then cause the affected system to become non-responsive and restart.

An attacker could also make a specially crafted file available on a Web site. An attacker would have no way to force users to visit a particular Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability? 
Any system that uses the Microsoft Malware Protection Engine is at risk from this vulnerability.

What does the update do? 
The update removes the vulnerability by modifying the way that the Microsoft Malware Protection Engine processes files.

When this security bulletin was issued, had this vulnerability been publicly disclosed? 
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited? 
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.

Microsoft has not identified any mitigating factors for this vulnerability.

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

• Microsoft Forefront Security for Exchange Server, Microsoft Forefront Security for SharePoint, and Microsoft Antigen support multiple engines in addition to the Microsoft Malware Protection Engine on a single system. If multiple engines are available on an affected system, administrators can disable the Microsoft Malware Protection Engine as a workaround, until the Microsoft Malware Protection Engine can be updated. Before disabling the Microsoft Malware Protection Engine, administrators should ensure they have installed the latest virus signatures for any third-party engine.
• We have not identified any workarounds for Windows Live OneCare, Microsoft Windows Defender and Microsoft Forefront Client Security.

What is the scope of the vulnerability? 
A denial of service vulnerability exists in the way that the Microsoft Malware Protection Engine parses files. An attacker could exploit the vulnerability by constructing a specially crafted file that could cause a denial of service when received by the target computer system and scanned by the Microsoft Malware Protection Engine. The denial of service results in disk-space exhaustion. After the Microsoft Malware Protection Engine has restarted, the temporary files that were created are deleted.

What causes the vulnerability? 
The Microsoft Malware Protection Engine does not properly validate certain data structures when parsing files. This can cause disk-space exhaustion, leading to a denial of service condition.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could fill up a system’s disk space, making the system slow or unresponsive.

How could an attacker exploit the vulnerability? 
An attacker could try to exploit the vulnerability by creating a specially crafted file and forcing an affected system to process the file. When the Microsoft Malware Protection Engine on the target machine automatically scans the file, the file could then cause the affected system to create large temporary files, filling up the system’s disk space.

An attacker could also make a specially crafted file available on a Web site. An attacker would have no way to force users to visit a particular Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability? 
Any system that uses the Microsoft Malware Protection Engine is at risk from this vulnerability.

What does the update do? 
The update removes the vulnerability by modifying the way that the Microsoft Malware Protection Engine processes files.

When this security bulletin was issued, had this vulnerability been publicly disclosed? 
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited? 
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.

Prerequisites
This security update requires Windows Live OneCare.

Restart Requirement

This update does not require a restart. The installer stops the required services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason, or if required files are being used, this update will require a restart. If this behavior occurs, a message appears that advises you to restart.

For more information about the reasons why you may be prompted to restart your computer, see Microsoft Knowledge Base Article 887012.

Removal Information

This update cannot be uninstalled when using Windows Live OneCare.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. Click Change Settings, then click the Logging tab.
2. Click Create Support Log button.
3. Under Virus and Spyware Protection Status, and Virus and Spyware Versions, the AM Engine should read 1.1.3520.0 or above, if the update has been successfully installed.

Prerequisites
This security update requires Microsoft Antigen for Exchange.

Restart Requirement

This update is automatic and does not require a restart.

Forefront Server security update service automatically updates the Microsoft Malware Protection Engine in Microsoft Antigen for Exchange Server. However, on computer systems running Microsoft Antigen where users have disabled the Microsoft Malware Protection Engine, users will have to re-enable the engine through the administrator tool. Once re-enabled the engine should be updated by clicking Update Now.

Removal Information

This update cannot be uninstalled.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. In Antigen Administrator, click Scanner Updates and then click Microsoft Antivirus.
2. Check the version number. If the Microsoft Malware Protection Engine build number reads 0.1.13.192 or above, the update has been successfully installed.

For instructions on configuring Microsoft Antigen, visit the following Microsoft Web site.

Prerequisites
This security update requires Microsoft Antigen for SMTP Gateway.

Restart Requirement

This update is automatic and does not require a restart.

Forefront Server security update service automatically updates the Microsoft Malware Protection Engine in Microsoft Antigen for SMTP Gateway. However, on computer systems running Microsoft Antigen where users have disabled the Microsoft Malware Protection Engine, users will have to re-enable the engine through the administrator tool. Once re-enabled the engine should be updated by clicking Update Now.

Removal Information

This update cannot be uninstalled.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. In Antigen Administrator, click Scanner Updates and then click Microsoft Antivirus.
2. Check the version number. If the Microsoft Malware Protection Engine build number reads 0.1.13.192 or above, the update has been successfully installed.

Prerequisites
This security update requires Windows Defender.

Restart Requirement

This update does not require a restart. The installer stops the required services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason, or if required files are being used, this update will require a restart. If this behavior occurs, a message appears that advises you to restart.

For more information about the reasons why you may be prompted to restart your computer, see Microsoft Knowledge Base Article 887012.

Removal Information

This update cannot be uninstalled from Windows XP or Windows Server 2003.

This update can be uninstalled from Windows Vista.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. Click Help, then click About Windows Defender.
2. Check the version number. If the Microsoft Antivirus engine build number reads 1.1.3520.0 or above, the update has been successfully installed.

Prerequisites
This security update requires Microsoft Forefront Client Security.

Restart Requirement
This update does not require a restart. The installer stops the required services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason, or if required files are being used, this update will require a restart. If this behavior occurs, a message appears that advises you to restart.

For more information about the reasons why you may be prompted to restart your computer, see Microsoft Knowledge Base Article 887012.

Removal Information

This update cannot be uninstalled when using Microsoft Forefront Client Security.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. Click the down arrow next to the Help icon, and then click About Microsoft Forefront Client Security.
2. Check the version number. If the Engine Version number reads 1.1.3520.0 or above, the update has been successfully installed.

Prerequisites
This security update requires Forefront Security for Exchange Server.

Restart Requirement

This update is automatic and does not require a restart.

Forefront Server security update service automatically updates the Microsoft Malware Protection Engine in Forefront Security for Exchange Server. However, on computer systems running Forefront Security for Exchange Server where users have disabled the Microsoft Malware Protection Engine, users will have to re-enable the engine through the administrator tool. Once re-enabled the engine should be updated by clicking Update Now.

Removal Information

This update cannot be uninstalled.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. In Forefront Administrator, click Scanner Updates and then click Malware Engine.
2. Check the version number. If the Microsoft Malware Protection Engine build number reads 0.1.13.192 or above, the update has been successfully installed.

For instructions on configuring Forefront Server Security for Exchange Server engines, visit the following Microsoft Web site.

Prerequisites
This security update requires Forefront Security for SharePoint.

Restart Requirement

This update is automatic and does not require a restart.

Forefront Server security update service automatically updates the Microsoft Malware Protection Engine in Forefront Security for SharePoint. However, on computer systems running Forefront Security for SharePoint where users have disabled the Microsoft Malware Protection Engine, users will have to re-enable the engine through the administrator tool. Once re-enabled the engine should be updated by clicking Update Now.

Removal Information

This update cannot be uninstalled.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. In Forefront Administrator, click Scanner Updates and then click Microsoft Malware Protection Engine.
2. Check the version number. If the Microsoft Malware Protection Engine build number reads 0.1.13.192 or above, the update has been successfully installed.

For instructions on configuring Forefront Server Security for SharePoint engines, visit the following Microsoft Web site.

Prerequisites
This security update requires Diagnostics and Recovery Toolset 6.0 and affects the Standalone System Sweeper.

Restart Requirement

This update does not require a restart.

Ensure that you have installed the latest definitions before starting a scan using the Standalone System Sweeper located on the ERD Commander Boot Media (DaRT bootable CD). To update definitions, launch the Standalone System Sweeper, and click the Down Arrow next to the help icon, and choose Check for updates. Follow the instructions to check for definition updates.

If you have created ERD Commander Boot Media (DaRT bootable CD) prior to May 13, 2008, you should discard it and create new media for future scans using the Standalone System Sweeper.

Removal Information

This update cannot be uninstalled.

Verifying Update Installation

To verify that the update has been applied to an affected system, perform the following steps:

1. Launch the Standalone System Sweeper, click Down Arrow next to the help icon and then click About Standalone System Sweeper.
2. Check the version number. If the Microsoft Malware Protection Engine build number reads 1.1.3520.0 or above, the update has been successfully installed.