An update to Microsoft Security Essentials is marking Claymore's miner 12.5 as a virus and shutting it down automatically. what should I do?
If the exemptions wont make it, try to roll back updates
and if you are not actually keen or conservative about latest Microsoft update releases
better not to do an update or disable it
some threads
https://bitcointalk.org/index.php?topic=2878646.0