Just another thought in relation to Q's "Update 816093 was installed last August. Has 'Trojan' evolved?" which may be way of the mark...

As far as I understand it, it is quite possible to have more than one Java machine on a system. I have Sun's Java 2, v 1.4.1_01 on this PC and according to my control panel settings that currently makes that the default plugin for both IE and Netscape. Presumably that means it overrides the MS Virtual Machine(VM)

John's comments which I will paraphrase as "a schoolkid with a few hrs of computer experience could modify malicious software" of course still stand.