Transparent Proxy Authentication using NTLM
Some web-browsers (mainly Internet Explorer) support NTLM authentication. This is a non-standard connection-based authentication system so it is not widely supported.
If enabled, then the NetManager will authenticate incoming proxy connections against a Windows domain controller (assuming the proxy is configured to request authentication which it is not by default). This should happen transparently, i.e. the user will not see a login box.
If your domain controllers are slow to respond or you do not have an Active Directory domain, you can enable NTLM identification. This retains the same communication between the client browser and the NetManager, but does not check any details with a domain controller, i.e. it just trusts whatever the client says.
N.B. As NTLM is non-standard, it may cause problems with any non-IE browser or program wanting web access. This extends to software trying to check for updates and Java applets.
In the Proxy-Filtering configuration section of webadmin, add an access rule of Blocked if not logged in. This will force all requests to be authenticated by using standard proxy authentication (i.e. manually entered and then checked against NetManager or Active Directory passwords).
Next go to the Web Proxy > Settings section of webadmin and enable either the option Attempt NTLM authentication and fall-back to Basic if necessary or Use NTLM identification.