On Dec. 23 we were made aware of a new claim of a vulnerability in Internet Information Services (IIS). We are still investigating this issue and are not aware of any active attacks but wanted to let customers know that our initial assessment shows that the IIS web server must be in a non-default, unsafe configuration in order to be vulnerable. An attacker would have to be authenticated and have write access to a directory on the web server with execute permissions which does not align with best practices or guidance Microsoft provides for secure server configuration. Customers using out of the box configurations and who follow security best practices are at reduced risk of being impacted by issues like this.
Once we’re done investigating, we will take appropriate action to help protect customers. This may include providing a security update through the monthly release process, an out-of-cycle update or additional guidance to help customers protect themselves.
This vulnerability was not responsibly disclosed to Microsoft and may put customers at risk. We continue to encourage responsible disclosure of vulnerabilities as we believe reporting vulnerabilities directly to a vendor serves everyone's best interests. This practice helps to ensure that customers receive comprehensive, high-quality updates for security vulnerabilities without exposure to malicious attackers while the update is being developed.
I want to close by providing some resources and best practices for securely configuring IIS servers:
IIS 6.0 Security Best Practices
Securing Sites with Web Site Permissions
IIS 6.0 Operations Guide
Improving Web Application Security: Threats and Countermeasures
*This posting is provided "AS IS" with no warranties, and confers no rights*