It was a bit difficult figuring all this out, but with the help of a few admins here I got it all working.
Here's the URL to the guide, have fun!
http://www.tcptechs.com/opnsense-transparent-caching-filtering-proxy-with-virus-scanning/
Your guide is dead - see attachment
Sorry it should work for most now. I got a little over-eager on the restrictions not long ago :)
Be careful with your tutorial. Your landing page is vulnerable to at least XSS.
I assume you mean the Antivirus landing page due to echoing the GET vars... I'll update that in a bit; it was a quick and dirty I forgot about fixing.
The landing page in the guide has been updated, it's no longer vulnerable to XSS. Also I found another step I had forgotten: To enable httpd to start at boot. That's been fixed too.
Edit: Just updated guide with 10th step to enable firewall and SELinux.
Awesome man, I was looking to implement this. This will come handy. I will implement this once I get back my firewall box. Have you tried this method with other iCAP AV engines?
Thanks,
Bobby Thomas.