Microsoft Forefront Threat Management Gateway (TMG) 2010 may not block some websites that have more than one category assigned to them. This update adds a For URL filtering, apply to non-primary categorizations option to Forefront Threat Management Gateway (TMG) 2010 Service Pack 1 (SP1). This option adds support for secondary categories of URLs.
To resolve this issue, install the software update that is described in the following Microsoft Knowledge Base (KB) article:
2288910 Software Update 1 for Microsoft Forefront Threat Management Gateway (TMG) 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the non-primary categorizations option for URL filtering, visit the following Microsoft website: