"As part of regular update of our antimalware technology to address the latest in the threat landscape, MMPC is planning to release a new antimalware engine on 18 Oct 2011.
Affected products: Microsoft Security Essentials, Forefront Client Security, Forefront Endpoint Protection, Windows Intune Endpoint Protection.
Engine Version will be in the range of 1.1.780x.0"
Source:
New Antimalware Engine is planned for release on 18 Oct 2011 - Antimalware Engine Notifications - Site Home - TechNet Blogs