Microsoft has become aware of two interrelated issues affecting a Manual Scan in Forefront Security for SharePoint.
The first issue is a memory leak which occurs when Keyword Filtering is enabled. In all versions of Forefront Security for SharePoint prior to Service Pack 3, whether you have Keyword Lists created or not, you may experience this issue. If, however, you have Forefront Security for SharePoint with Service Pack 3 installed (released 7/1/2009), this issue will only occur if you have Keyword Lists created. If you do not have any Keyword Lists, even if Keyword Filtering is enabled for Manual Scan, you will not experience the leak. Real-time scanning is not affected by this issue.
The second issue may occur as a result of the first. After a period of time the memory leak can cause memory allocations to fail. If these failures occur repeatedly in a specific way, it causes Forefront Security for SharePoint to incorrectly determine a valid document as “exceedingly nested”. Every file that is scanned and determined to be exceedingly nested will be deleted and the contents replaced with standard deletion text.
Microsoft is actively working toward a resolution for these issues. An update will posted as soon as more information becomes available. In the meantime, we recommend that any customers using Forefront Security for SharePoint that run a Manual Scan disable Keyword filtering for Manual Scanning (for more information on configuring the Manual Scan job, see "Running the Manual Scan Job" in the FSSP User Guide http://technet.microsoft.com/en-us/library/bb795164.aspx). This is extremely important, as manual scanning of your entire document library opens the potential of losing any document content incorrectly identified as “exceedingly nested”. Please note that, by default, Keyword Filtering is enabled for the Manual Scan job.
Microsoft Forefront Escalation Engineer