I apologize if this is vague/incoherent; I'm a newbie to Windows Admin.

I have a Windows 2003 file server that shares several SMB shares.
Currently I have the SMB digital signatures turned on. I have tried to
mount those shares from a Mac OS X (10.3 and 10.4) client and it fails.
I tested the following suggestion of turning off the signing and it
worked.

http://www.experts-exchange.com/Netw..._21024387.html

I am curious what turning this off does. It appears to prevent some
sort of SMB attack and introduces a 10-15% performance hit. The
questions I have

1. Are passwords still encrypted or are they now plain text (were they
always plain text)?
2. What other security risks do I run by disabling this feature?

Thanks in advance.