In N+1 magazine, David Auerbach explains what it was like in the "Chat Wars" of the late '90s, when he was the youngest person on the team developing Microsoft's brand-new messaging app, in the face of America Online's AIM, the 900-pound gorilla in the room. Auerbach explains how he used a network analyzer to fake out AOL's servers
into letting Microsoft's client connect to AIM as well.
"AOL could only block Messenger if they could figure out that the user was using Messenger and not AIM. As long as Messenger sent exactly the same protocol messages to the AOL servers, AOL wouldn’t be able to detect that Messenger was an impostor. So I took the AIM client and checked for differences in what it was sending, then changed our client to mimic it once again. They’d switch it up again; they knew their client, and they knew what it was coded to do and what obscure messages it would respond to in what ways. Every day it’d be something new. At one point they threw in a new protocol wrinkle but cleverly excepted users logging on from Microsoft headquarters, so that while all other Messenger users were getting an error message, we were sitting at Microsoft and not getting it. After an hour or two of scratching our heads, we figured it out."
Eventually, though, AOL introduced x86 assembly code into the login protocol, and that not only stymied the MSM team, but led to some interesting warfare of its own. Auerbach's story sheds a lot of light on both good and bad aspects of corporate culture at the start of the 21st century, at Microsoft as well as other companies.