When run the trojan installs itself to the system. While installing the trojan copies itself to Windows, Windows system or TEMP directory and registers itself in system registry auto-run section. For example:
Trojan's full name:
WindowsAgent = winzipauto.exe
The installed trojan file name, the target directory are optional. They are stored in encrypted form in trojan file at the file end. To steal OICQ data the trojan also drops additional DLL file (hooker) with optional name. A hacker may configure optional data before sending trojan to a victim machine, or before put it on a web site.
There other optional features of this trojan:
display decoy (fake) messsage, and the message text
delete original file after installing into the system
email address to there stolen data is being sent (default - email@example.com)
smtp server to there the data is being sent (default - smtp.sina.com.cn)
The trojan then registers itself in the system as hidden aplication (service), the trojan process then is not visible in task list. Being active in the system trojan periodically sends email messages to its host (hacker's email address).
There are known "upgrated" version of this trojan that do mail themselves, and are "Internet worms" as a result. See the description of Gop worm.