There are a number of Private query blockers that have been scripted and will handle things like this.
Basically how they work is that they block pm/query messages from all users unless you have pre-authorized the user.
Some will allow you to decide if you want to allow the user upon receipt of their first message.
You can look for these scripts on sites like
Hawkee,
mIRC.net,
mIRCScripts.orgIf you just want to completely ignore any and all private messages, then you can simply do /ignore -pw *!*@*
The p switch makes it ignore private messages, and the w switch makes it for all networks. If you don't specify the w switch, then you will only ignore private messages on your currently active network.
BTW: People can't infect your computer remotely for you not leaving a room. You would have to accept a file transfer from them first.
If (and I doubt this) a channel op tells you to leave and you don't, then they have the authority and ability to kick and/or ban you from the channel. Most ops will ask you to leave via a post in the channel, and I don't know of any channel op that would resort to threatening virus infection if you didn't leave.