Antimalware Engine 1.1.9800.0 was released to customers on 20 Aug 2013

Antimalware Engine 1.1.9800.0 was released to all Microsoft Security Essentials, Forefront Client Security, Forefront Endpoint Protection, and Windows Intune Endpoint Protection customers on 20 Aug 2013. Signature package 1.157.0.0 is the first that contains this engine.