This indicates an attack attempt against a Denial of Service vulnerability in Microsoft Network Policy Server.
The vulnerability is caused by an error when the vulnerable software handles a maliciously crafted Access-Request packet. It allows a remote attacker to crash vulnerable systems via a crafted Access-Request.
Microsoft Windows Server 2008
Microsoft Windows Server 2008 R2
Microsoft Windows Server 2012
Microsoft Windows Server 2012 R2
Denial of Service: Remote attacker can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor