According to Twitter user @Chpwn (thought to be a member of the Dev-Team), Apple has blocked all access to Amazon servers which identify themselves under gs.apple.com, used to authenticate SHSH certificates for App Store alternative, Cydia.
The tweet read:
Apple has blocked all of Amazon (where @saurik’s SHSH servers are hosted) from accessing gs.apple.com (Apple’s SHSH server). /cc @notcom.
Essentially, this means that users can no longer connect to Saurik’s servers which host Cydia, and therefore are no longer able to obtain the certificate necessary to verify an earlier version of their firmware. While @Saurik is yet to confirm the move himself, iSpazio notes that the move may hinder the jailbreak process long enough for Apple to catch up on developing and deploying security methods in both iTunes and the next release of iOS.