Block HTTP(S) Traffic Over Non-Standard Ports

In Transparent mode, only TCP 80 and 443 ports are intercepted by Web Filtering module. All other traffic is redirected to firewall packet filtering.

Conclusion is to avoid having "LAN -> ANY -> InternetV4" firewall rule in combination with Web Filtering in Transparent mode.

So basically, for every outbound firewall entry (other than 80 & 443) I need to only allow access to specified hosts?

Correct.
Below you can see firewall rule example from one of my client's production UTM9 environments, using Web Filtering in transparent mode with request to allow access to local radio station that is broadcasting on non-standard TCP ports:

Okay thanks for that. Here's the next hurdle... I am currently allowing outbound traffic over ONLY 80/443 yet applications like Ultrasurf are still able to completely bypass the filtering (I also have application control set up to block it...)

UTM should recognize Ultrasurf in application control module.

Hi,

do you have ATP enabled, that should stop a  lot of that strange traffic?

The other alternative to Vilic's suggestion is to add those ports to the transparent proxy and tick the do not scan streaming media.

Jeremy, one of our unwritten rules here is "one topic per thread."  That makes it easier for future Community members to find answers to their questions faster and without bothering to ask a question that's been answered.

Cheers - Bob

Oh because now we're taking about a different way to bypass the filtering... Gotcha. I can open up a new thread as I continue to work through this issue.