This indicates an attack attempt against a remote Code Execution vulnerability in Microsoft Office.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted RTF file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted RTF file.
Microsoft Office 2007
Microsoft Office 2010
Microsoft Office 2013
Microsoft Office 2013 RT
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.