I was running a routine security check of the machines I manage today and found in my nmap scans that TCP/554 is open, although when I run 'netstat -an' on the machine itself it doesn't show up, same result if I nmap the host locally.
I then tried connecting to www.google.com on tcp/554 and it is open and it seems all hosts 'have the port open'.
Obviously my ISP is doing something here but then I tried the same on my iphone via a 3G connection and it returns the same results. My ISP is a satellite ISP and my phone/3G connection is with a totally separate provider. Any ideas ?