Symantec port scan detects an open port - how do I stealth it?

I ran Symantec Security Check from their website and it reported that a trojan attack would be possible via port 4567 - the “shields up” site also confirms that this port is open.

All my other ports are stealthed.

How do I stealth this one?

Apologies for the VERY basic question!!!

I did not edict any specific rule for whatever port, outside of forbidding 135-139 and 445 on the WAN side and limiting applications types to the minimum (e.g., 80 and 443 for http, 25 and 110 for mail…).

I am nevertheless said (for what it might be true…) safe from Symantec, Grc, Pc Flank…

Some explanation could be found via ActiveX and, thus, Internet Explorer: i do not use IE, i forbid ActiveX, and scripting abilities by Firefox, No Script, and surveying Cookies potentialities.

Another issue could be found by the penetration not of the computer itself, but of a badly securized home router providing the connexion and being indeed tested rather then the computer itself.