Customers running Microsoft Forefront and Antigen products will required to take steps in order to optimized protection as Microsoft is revising its engine mix on Dec. 1, 2009. “AhnLab, CA, and Sophos engines’ll be retired on Dec. 1, 2009. After December 1st, customers’ll not receive any updates for these retired engines. In order to make sure your Antigen and Forefront products continue to scan efficiently and effectively for malware, any customers running AhnLab, CA, or Sophos engines must DISABLE these engines before Dec. 1, 2009 and select from new set of five engines – Authentium, Kaspersky, Microsoft, Norman, and VirusBuster.”

More info: Forefront blog.