This indicates an attack attempt against a remote Code Execution vulnerability in Microsoft Internet Explorer 8.
The vulnerability is caused by an error when the vulnerable software handles a certain COM object that is instantiated as an ActiveX control. It allows a remote attacker to execute arbitrary code via sending a crafted web page.
Windows XP Service Pack 2 and Windows XP Service Pack 3
Windows XP Professional x64 Edition Service Pack 2
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Vista Service Pack 1 and Windows Vista Service Pack 2
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 7 for 32-bit Systems
Windows 7 x64 Edition
Windows Server 2008 R2 for x64-based Systems**
Windows Server 2008 R2 for Itanium-based Systems
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch, available from the vendor's website: