You can, on IRC, see which IP belongs to
a user (whatever you need to know this for, obviously 
).
This is achieved, inside mIRC, with the /dns command. So, for example, if
you want to know what IP is using your channelmate Jogi you can do:
/dns Jogi
and you will see, after some time, the IP and the IP name (if there is one) of Jogi in the Status window. So, what's he big deal you'll ask, a page just for this command? Not actually, because it may be annoyng to switch to the Status window every time you need to check the IP of a user. So here we'll make a script which will send a message to our current channel window with the regarding information.
You can use this addon to load the script from within mIRC, instead of writing the lines yourself.
If you want to add the lines yourself, here are the instructions.
Before we begin, let's recall that you need
to press the button 
in
mIRC to access the Remote panel, that is where you edit scripts.
What you need to write there is:
on *:DNS://echo -a Resolved $nick to: Name - $naddress , IP - $iaddress
and the output, after you add this line, press OK,
and issue the /dns command on a user, will appear in the active window, and
resemble this:
Resolved Joey42 to: Name - co3061808-a.eburwd1.vic.optushome.com.au , IP - 203.164.127.151
In the case the IPname was not available, the field after "Name -" would simply be empty.
You can check with this also the IP corresponding to websites. For example, if you want to know what IP is associated with www.microsoft.com just do:
/dns www.microsoft.com
and the output will be:
Resolved to: Name - www.microsoft.com , IP - 207.46.230.219
and as well see what IP name belongs to an IP you run into:
/dns 65.92.216.192
the output being:
Resolved to: Name - HSE-Montreal-ppp3473182.sympatico.ca , IP - 65.92.216.192
clear enough I'd say.
Now go on IRC and play a bit 
.