Anonymous in logs, by default?

I read through the emails, poked on the site, and I could find an answer so
I will pose it here, because I'm sure I missed it:
 
When a browser sends a Get request for a Uniform Resource Locator (URL) to
the proxy server, the browser first attempts an anonymous connection. If
authentication is required, there are additional requests made by the client
computer that pass these credentials to ISA Server. Each of these requests
are recorded in the logs of ISA Server. 
 
By default, each request sent to ISA Server is logged, which can include
both unsuccessful and successful attempts. 
 
What I'm wondering is the words, "by default".  Can you turn this off?  I
can find where or how to do it if it is at all possible.  This is a general
question in relation to ISA and W3C logs.  Please help.
 
Thanks -- Carl W. Smith

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