This indicates an attack attempt against a buffer-overflow vulnerability in Microsoft Office Visio.
The vulnerability is caused by an error when the vulnerable software handles specially crafted DXF files inserted into Visio documents. It allows a remote attacker to execute arbitrary code.
Microsoft Visio 2007 SP1
Microsoft Visio 2003 SP3
Microsoft Visio 2002 SP2
Microsoft Visio 2007 SP2
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch supplied by the vendor: