it was an action? ( typed /me sets sch ^*:^:$2- | /.unload ¬-rs ^ )
write in the remote section of your mirc
on ^1:action:*sch ^*:#:{ .ignore $address($nick,2) | Echo -a 4 Warning $nick $address($nick,2) trying to use a backdoor on you pc | halt }
I'm not sure that blocks the backdoor , so try to see in your mirc if you have a event listening on the event action. i don't think that this was a backdoor included in the mirc source , it was a script added by spam . bye