Port 0

[Anno Domini]

Haha I love Kerio 2.1.5 and appreciate you remembering the good times, JJoe. :-) I still use it because of its great outbound control and configurability and because I still have WinXP and Win7. I have searched and searched for another firewall that could alert me like Kerio does when something wants out and the only one I could find close to it is the Comodo 5 series and the versions before. Comodo 5 works on Win7, Kerio 2.1.5 does not. There's also a way to decrease the installation size of Comodo by just installing the firewall and defense+, but we're getting sidetracked.

I took your advice and examined my rules in Kerio 2.1.5 and I don't know if I can explain this because I don't understand it, but I noticed my loopback rule for Proxomitron was UDP outbound only and my alert for Proxomitron trying to connect out on port 0 was for TCP. See attached photos. I blurred some parts for security. My rules are from a ruleset called "BZ Kerio 2x Default Replacement - Advanced - Final." (see attached photo). Note that BZ has a standard and advanced Kerio ruleset. The photo I attached is BZ's advanced rules and the one I use. I don't understand how the proxy loopback works, but after you suggested I double check the local proxy configuration in Kerio, I noticed my loopback rule was UDP out only. So I changed it to UDP + TCP out (see attached photo) like BZ's advanced software proxy loopback rule. Now the alerts from Proxomitron trying to connect out on port 0 with TCP are gone. My firewall now says, "TCP Connection to (null) [127.0.0.1:0] was permitted by rule 'Loopback for Proxy (out)." I don't understand it JJoe, but thank you for leading me to the source. You are a genius, but is this safe. Do you think I opened up a new security hole ?

BZ Kerio 2x Default Replacement Update
https://www.dslreports.com/forum/r802370...ent-Update