It's PSNPatch which has a option for Cobra firmwares to spoof. With a change to the config file it can also successfully spoof to 4.70, however only for cobra fws.
I'm currently trying to do a spoofer for 4.66 and 4.65 systems, however these freaking 8 new certificates are annoying me.
I spoofed to 4.70 successfully, however my PS3 tells me the error code 80710101 (no internet connection) when trying to get into PSN, I guess this has to do with the certs...