Problem with remote authenticated access to web application

[David Gómez Gómez]

I have a web app running con COMPUTER1 called Proyectos. In web.config i
have windows integrated authentication and:

<authorization> <allow users="COMPUTER1\John" /> <allow
users="COMPUTER1\Liz" /> <deny users="*" /></authorization>

COMPUTER1 (XP Pro SP2) and COMPUTER2(win98) are connected and conform a
workgroup named WORKGROUP (I know, be more inventive). John and Liz are
accounts on COMPUTER1. COMPUTER1 is connected to the internet (and sharing
this connection) with an IP, let's say 84.178.55.125, and is also
identificated over the inet as computer1.dyndns.org.

Usually John logs in COMPUTER1 and Liz in COMPUTER2. Whenever any of them
asks for http://COMPUTER1//Proyectos, they will get access to the web app
without any further problem. But when trying http://84.178.55.125/Proyectos
or http://computer1.dyndns.org/Proyectos, none of them will get access
(integrated auth. login box appears, but acces is not granted).
Neither will them from any computer outside the local network. When
anonymous login is allowed (simply removing the deny users tag) there's, of
course, no problem form inside or outside the network.

Can anyone tell me what am I -or is my system- doing wrong? Do I have to
configure anything within integrated firewall? Is it possible that i have
disabled any necesary service for remotely accesing my web app? Any missing
permission for users to check?

Thanks in advance.

 

[David Gómez Gómez]

Just a little update: everything will work fine if i turn on Basic auth
within IIS for the web application, setting domain name as "COMPUTER1", and
keep integrated windows auth. unchecked. But this is unsecure, isn't it?
What can I do to get integrated auth. to work, so avoiding plain text
password transfers?