Many people ask the question (Customers, on TechNet Forums, …) and on Forefront Endpoint Protection TechNet documentation - we don’t find the name of the file.
People who worked on Forefront Client Security know the file because it is the same.
Location: %allusersprofile%\Microsoft\Microsoft Antimalware\Support
Name: MPLog-XYZ.log (XYZ is the date)
Ed Price - MSFT edited Original. Comment: Tag