From Mibbit Wiki
How webirc works:
- The user opens a mibbit client and requests a connect to, e.g., irc.blah.com
- The Mibbit backend checks irc.blah.com for matches in mibbit's webirc database
- If found the backend sends the webirc tag along with the user's IP and the password (chosen by the server admin) to irc.blah.com. The client's server tab shows the network name as saved in the database, e.g., "BlahNET".
- The server (irc.blah.com) checks all requests from 188.8.131.52, 184.108.40.206, 220.127.116.11 and 18.104.22.168 (ircip1 .. ircip4.mibbit.com) for the correct password and then converts ident to "Mibbit" and @*.mibbit.com to the user's host name (most networks obfuscate the host for non ircops). The network thus allows an (almost) unlimited number of users from Mibbit's IPs and makes ban evasion etc less easy.
- When webirc works properly for irc.blah.com ircops should set a friendly "/gline *@ircip*.mibbit.com - Please use only irc.blah.com to connect our network" (or similar) to avoid ban evasion etc by people using your IP(s) or rDNS or even letting their own DNS/CNAME point at your server(s).