Microsoft Security Essentials antimalware definitions are now available via WSUS. Microsoft Security Essentials is a core antimalware service for consumers and home-based small businesses that Microsoft released in September of 2009. This was done because academic institutions around the world (particularly in Asia) provide students with low cost or free internet access and provide students with update services through WSUS. Many students are protecting their computers with Security Essentials, and the universities requested that the definition updates be provided via WSUS.
With this change, there is a new product family (Microsoft Security Essentials) and product name (Security Essentials) WSUS in the admin console. Note that the addition of this product family and product name is only to accommodate the definition updates for Security Essentials. This is not a replacement or a rename for any current Microsoft a/v product.
MU and Microsoft Security Essentials teams