It isn't a trojan.
If you just decode the encoded message, you'll see that it is a plain ol text file with a .mrc extension, which the user (when running those commands) writes, saves, and loads into mIRC, which then, everytime someone joins, msg's them the exact same thing that the user originally got.
To be honest, the person that did this is just a complete fsckwit.
There was no "skill" involved.
And personally, I would reccomend ignoring all private messages excepting for services, and those you can trust.
/ignore -p *!*@* (ignores every private message)
/ignore -x nickname (excludes that nickname from the ignore feature, ie /ignore -x ChanServ would allow ChanServ to still private message you).
I'm on Austnet, and I simply have an on ^*:OPEN:? { } event that halts default text, closes each window as it opens, and then notices the nickname that I am ignoring queries. It doesn't use the /ignore feature, but it acts in a similar way.
