Bkdr_PoisonIV.QI is a backdoor that may be downloaded from remote sites by a malware detected by Trend Micro as EXPL_NEVAR.B.

It opens a hidden Internet Explorer window. It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user is able to execute commands on the affected system.

Technical details can be found at this Trend Micro page.