IRC (Internet Relay Chat)
acronymops culturehacking
The text chat protocol written by Jarkko Oikarinen in Finland in 1988: servers federate into a network, users join channels prefixed with #, and the whole thing is simple enough to speak by hand over a raw socket. Standardised late, in RFC 1459 and its successors.
IRC was where open source, the security underground and most of internet culture actually lived for two decades - Linux kernel work, warez trading, the Anonymous operations, and the first incident-response calls all happened in channels. Its bot ecosystem taught a generation to automate, then taught attackers the same trick: early botnets were literally IRC clients that joined a channel and waited for the operator to type commands, which is why so much command and control still looks like chat.
Also known as: internet relay chat, efnet, undernet, freenode, libera chat