Because of the security involved in Windows NT and 2000, every
user needs a username in order to connect to the server
and gain permission to do something. IIS
automatically sets up an account for the anonymous internet user
that starts with IUSR_ and ends with the machine name of the server.
The properties on this account specify what rights an
anonymous user to your web site has. Therefore it's
important to keep the permissions on this account
on a relatively tight string. If the account gets
permission to the wrong things it becomes a real
security breach and can result in anyone being able to
get at information on your server that you might not
really want to be public.
On the other hand, when you start getting "Access Denied"
problems in your scripts, it's often because the user
doesn't have enough rights. Figure out if it's something
you really want everyone to be able to do or not, but
either way, the IUSR_machinename is usually the account