Please see
this sticky thread. It's a good idea to read the stickies before posting, they answer the most common questions.
As for protecting yourself on IRC, it's very simple. Don't type what others tell you to type. Don't click on URLs other people spam to you. Don't accept files from strangers. Don't load scripts if you don't know what they do.
As you're getting this error message I can only assume you're using mIRC for file trading? If you are, then note that mIRC is not a file trading program and using it as one is opening your computer to the greater possibility of being infected.
For further info pertaining to your post, see
this thread and
this thread.
Regards,
