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 Trojan horse takes advantage of an old Windows 95/98 vulnerability. A Microsoft patch that fixes this vulnerability has been available since March 2000. The affected systems are Windows 95, Windows 98 and Windows 98 Second Edition (SE).