Trojans are malicious applications that pose themselves as legitimate software in order to trick users to install them. Once on the victim's machine, it may run any number of malicious process to steal vital information or inflict damage to other software.
QQMuma is a chinese trojan that attacks a victim's Image File Execution Options. It redirects critical system processes to the key infection file. This file is stored in c:\Program Files\Common Files\Microsoft Shared\.