This indicates an attack attempt against a code-execution vulnerability in Microsoft SMB Client.
The vulnerability is caused by an error when the vulnerable software handles a malicious SMB response. It allows a remote attacker to execute arbitrary code via sending a crafted SMB response.
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Server 2003 with SP2 for Itanium-based Systems
Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2
Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor's web site for the suggested workaround: