Closing an open http proxy

[Duane Morin]

I have a linksys router that passes port 80 requests to my server, which 
is running apache (1.3.x), which in turn uses ProxyPass/ProxyPassReverse 
to hand off /foo requests to localhost:8081 which is running a webapp 
called 'foo' using Tomcat.

This works just ducky.  Except I'm starting to get warnings saying that I 
have an open http proxy.

I'll happily fix it, I'm just not sure how.  The instructions I found seem 
to say deny access to the site to everybody except for specified domains, 
but that makes no sense to me, I want people to access my site.  

Duane