Trilight Zone

[digital8]

In IRC, it is possible to put yourself into mode x by typing '/mode yournick +x' (do not include the quotes and replace yournick with your own nick. For example: /mode raven +x).
This tells the IRC server to hide your IP, so when others try to /whois you or /dns you, they won't be able to get your IP (they will get a partial IP instead).
This will only work on some servers, but when you're on IRC, it is recommended to use this option.
Also, there is a way to bypass this. By simply creating a DCC connection with someone else (either a DCC chat or a DCC file transfer), you could then type 'netstat' (without the quotes) on either Unix or Windows/DOS and see what connections your computer is currently handling. One of them will be the DCC connection to that other guy.
Why is that? Because DCC stands for Direct Client Communication, which means that DCC actions are not done through the server, but directly (think - why would the owners of the IRC server want people to transfer files through their servers and initiate private chats through their servers? It'll just chew up some bandwidth). The netstat command shows all current connections (local or remote), and one of them will be your DCC connection with that other guy. You will then be able to see his/her IP or hostname.
Note: on some networks this is done by typing /mode yournick +z