There are tons of sites that will report you the public IPv4 address they see when you connect to them. Not a big deal. Personnally I will prefer getting this info from a known secure site rather than an unmanaged site or a commercial site that wants to sell you their security solution (using sometimes fake reports...)
Anyway, the "ShieldsUp!" port scan finds nothing on my PC, except its public IPv4 address, and it does not test the IPv6 address through which the test could be reached (does grc.com have an IPv6 address that I can connect to?).
Most personal firewalls today don't handle the IPv6 trafic, and won't block the IPv6 traffic, so port scans via IPv6 used by malwares may still find many more vulnerable clients than with IPv4. With the growing number of Internet users that have an IPv6 connection (even through a tunnel), this may be a concern.
Sometimes, some ISPs did not inform their customers before activating the IPv6 connectivity, this is the case of my ISP, and I noticed it working through a new tunnel only weeks after the change of its router firmware. How lame they can be ! Thanks I was not attacked, because I had previously already used some third-party Teredo tunnels, and preconfigured and checked my security, but may be the Teredo tunnel broker was implementing the firewall itself, but not my ISP.
So I had to check this again to see if I was vulnerable through this new unnoticed tunnel; it looks like my ISP filters (on its Cisco L2TPv2 tunnel) only a few wellknown ports used by Windows file/printer sharing, and outgoing SMTP connections, but nothing else (and there's no IPv6-to-IPv6 NAT: this is a lame bridge sharing data between distinct customers connected to the same L2TPv2 tunnel-broker, which also has severe bugs such as loosing essential IPv6 routing options needed for IPSEC, no longer working; my ISP has now suspended its experimentation and no longer adds new customers; Cisco will have to rework its bogous solution, or my ISP may use another technology for its final deployment)...
I can't edit or delete it, as we're only allowed 15 minutes to do so. Perhaps one of the moderators could do it.
I've deleted it.