Bounce Path Control
From Halopedia, the Halo wiki
Before each server was opened the Bounce Path Control page was active. This page prompted visitors to enter a verification code that the site listed. Once the code was entered the visitors were taken to a page that had "The Past" that linked the visitors to a mp3 file, "The Key" that had a 23 digit code, and "The Path" that linked the to send the key onwards. The first 100 people to enter the codes during the 5 times this page was active were presented with rewards.
Server 1 (Transmission061607.mp3)
Server 2 (3rd_MB-v4.mp3)
Server 3 (Transmission_072507.mp3)
Server 4 (mb_4_v6.mp3)
Server 5 (MB_5.MP3)