Without any back story My questions is how are credentials being passed across the network when a computer joins the domain during operating system deployment? By credentials I mean the account and password each machine is using to join the domain?

It's not really OSD that does this, it's Windows setup. I would assume securely using NTLM but that is probably a better question for a Windows forum. Note that to my knowledge, the actual password is never trasmitted across the network for any network activity. Hashes are created using the password on both sides and the requestor transfers the hash to the authority which then compares the hashes (it's a little more complx than that). Here's a (seamingly) good article that covers this: http://www.windowsecurity.com/articles/Protect-Weak-Authentication-Protocols-Passwords.html.Jason | http://myitforum.com/cs2/blogs/jsandys | Twitter @JasonSandys