Troj_Agent.QTR is a Trojan that may be downloaded from remote sites by other malware. It may be dropped by other malware. It maybe installed manually by a user. It may be downloaded unknowingly by a user when visiting malicious Web sites.

It drops a file that Trend Micro detects as TROJ_ROOTKIT.EA. As a result, routines of the dropped Trojan are also exhibited on the affected system.

Technical details can be found at this Trend Micro page.