I can't get it to work. Here's exactly what I did:

1. Create a new Azure VM, Windows Server 2012.
2. RDP to the new VM
3. Download & Extract Squid for Windows (2.7.STABLE8)
4. Rename the conf files (squid, mime & cachemgr)
5. Add the following lines on the end of squid.conf

auth_param basic program c:/squid/libexec/ncsa_auth.exe c:/squid/etc/passwd.txt
auth_param basic children 5
auth_param basic realm Welcome to http://abcde.fg Squid Proxy!
auth_param basic credentialsttl 12 hours
auth_param basic casesensitive off
acl ncsa_users proxy_auth REQUIRED
http_access allow ncsa_users

1. Use http://www.htaccesstools.com/htpasswd-generator-windows/ to create passwd.txt
2. Test passwd.txt via c:/squid/libexec/ncsa_auth.exe c:/squid/etc/passwd.txt (success)
3. squid -z
4. squid -i
5. net start squid (No errors so far).
6. go to https://manage.windowsazure.com, Virtual Machines -> myVM -> Endpoints
7. Add Endpoint:

Name: Squid
Protocol: TCP
Public Port: 80
Private Port: 3128

That's it. Unfortunately, it doesn't work. I think I screwed something up at the endpoint? I'm not sure.. help?

EDIT: I'm testing it via Firefox -> Options -> Advanced -> Network, and the exact error is "The Proxy Server is refusing connections." I'm using my DNS as the Proxy server "abcdef.cloudapp.net" and port 80 (since that's my public endpoint).