Underworld have been long time contributors to the EFnet IRC Network.
Eris Free Network, better known as EFnet is one of the major IRC networks with over 40000 users. It is the modern-day decendant of the original IRC network.
Initially, most IRC servers formed a single IRC network, to which new servers could join without restriction, but this was soon abused by people who set up servers to sabotage other users, channels, or servers. In August 1990, the server eris.berkeley.edu remained the only one to allow anyone to connect to the servers.
A group of IRC server operators, with the support of Jarkko Oikarinen, introduced a new “Q-line” into their server configurations, to “quarantine” themselves away from eris by disconnecting from any subset of the IRC network as soon as they saw eris there.
For a few days, the entire IRC network suffered frequent netsplits, but eventually the majority of servers added the Q-line and effectively created a new separate IRC net called EFnet (Eris-Free Network); the remaining servers who stayed connected to eris (and thus were no longer able to connect to EFnet servers) were called A-net (Anarchy Network). A-net soon vanished, leaving EFnet as the only IRC network.
The server name is irc.underworld.no and is hosted by UNINETT, the academic network in Norway and maintained by the Underworld organisation.