From Portal Puzzle Wiki
The BBS is a component of the Portal ARG. It appears to be the most important part of the puzzle altogether.
>== Timeline ==
On March 1st, 2010, when the puzzle started, Portal players around the world discovered the BBS number (see Discovery below). Many began dialing with phones, causing the BBS to become busy to others, who were trying to connect the correct way. Additionally, nobody knew the correct login information.
What is a BBS?
A Bulletin Board System (BBS) is the term used for a system to handle message boards, much like the Internet forums we see today. Bulletin Board Systems were commonly used in the 1980s and early 1990s, before the widespread popularity of the Internet, as a means of communication. To access a BBS, one simply needs to call the BBS using a modem, through "terminal software," such as HyperTerminal.
This BBS was discovered from the SSTV pictures generated from the dinosaur wav files. Images 2, 6, 8, and 15 hinted at a BBS. Images 1, 3, 5, 10, 13, 14, 16, and 21 had seemingly random numbers and letters in them, but when put in the correct order, it gave an MD5 hash of 9459C6CAC8C203B8128B7CC63068D4FD. After thorough brute force attempts, the hash was cracked and revealed the number to the BBS.
IMPORTANT: Do not, under any circumstances, call this number with a telephone! The result is like calling a fax machine and you will hamper the efforts of those with the correct hardware and software to connect to the BBS.
While not a true BBS since it doesn't serve as a means of communication, the Portal BBS is accessed using a modem through a terminal. Once connected, the user is presented with a login prompt that reads 'GLaDOS login:' The user may then log in with the username/password: backup/backup. It will then give a seemingly random "dump" of files consisting of mysterious ASCII art images and memos from the late Cave Johnson. Before each file, an "error" is displayed, often humorous. It is confirmed that the error is linked to the file it precedes.
If left idle at the log in screen for 4 minutes, you are presented with a warning that reads "Hey! Please login now. You have one minute left" if left idle for another minute you are given the following message before disconnected. "Your login time (5 minutes) ran out. Goodbye."
The BBS will continue to output file data for about two minutes and twenty-three seconds before hanging up on the user. Additionally, the BBS's modem negotiates at only 1200 baud (or 150 bytes per second), which means very little data can be retrieved from each session.
This section is for information pertaining to Valve's implementation of the BBS.
The BBS is hosted in Kirkland, WA. It appears to be running mgetty (or another getty) or a very carefully crafted emulation of it (the BBS has displayed some very obscure strings such as "Hey! Please login now. You have one minute left")
It is likely a Linux or UNIX system. However, as it seems Valve has more firsthand experience with Linux than UNIX, they would likely opt to run the BBS on Linux. Its hostname is GLaDOS.
As seen above, the BBS's modem negotiates at a mere 1200 baud. Whether this is intentional on Valve's part (configuring the port to such a low rate) or due to a poor modem/connection is unknown at this time.