TROJ_MDROPPER.BO is a .doc file. it exploits a zero-day vulnerability in Microsoft Word 2000. No specific details yet on this vulnerability. This specially crafted doc file executes a shell code that drops and executes an embedded exe file. TROJ_MDROPPER.BO executes a backdoor that is being detected by Trend Micro as BKDR_PCCLIENT.PX. To protect your system from this threat please update you pattern file to 3.735.00.

You can manually download the pattern file here.

For more details on this threat, click here.