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.
This is a Trojan that installs a hidden executable file and .dat file in the system32 directory of the victim's PC. While running, it has the ability to manipulate mail in Outlook and specifically looks for Opera Mail usernames and passwords. It also makes connections through mIRC.