From Worms Knowledge Base
LeetF*ck is a now-obsolete connection program designed by Annelid during his 2003 program-making stint. Like most of his applications, it came about when he discovered something nifty could be done, and wanted a quick way to make it happen. LeetF*ck automatically determined a user's IP address upon initialization and forwarded the information to Worms Armageddon... a process handy back in the day for anyone with a dynamic IP address and a router who wanted to host games. (June 2007's W:A update now determines a client's true IP address in a more acceptable way, thus making this functionality unnecessary.)
But what everyone used leetF*ck for was the other feature... it set itself up as a local proxy on port 1337, and using a special serverlist link, Worms could be made to connect to WormNet through leetF*ck. The program then filtered various pieces of data from the communication, which could be used to display a custom rank (instead of the default lowest rank) or, most popularly, turn on the flaming power bars option in online games. These were effectively disabled in a beta in October 2004 (and completely disabled in March 2005) so are now also obsolete.