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.
Trojan.Zyn is trojan originating from China. It is commonly seen distributed through peer-to-peer channels such as Kazaa. Once infected, the user will be prone to more attacks and even potential identity theft. It sends several remote login requests to the victim's PC as well as tunnel http traffic.