There have been random reports from around the globe, that Cydia is blocked over 3G network. Several 3G providers around the world such as Ireland’s 3 and UK’s 3 have blocked access to Cydia as reported by Irish iPhone hacker and developer @stroughtonsmith via twitter.
Apparently China Unicom is also blocking access to Saurik’s Cydia servers. It is quite common for websites to be blocked in China, so many web users would subscribe to VPN service for their computers and iPhones to access blocked websites such as Facebook, YouTube or Twitter. Jailbreaking tool such as Limera1n, once installed on the iPhone, will not be able to download the Cydia package unless you have a VPN setup on the iPhone.
Jailbreakers will notice the issue when Cydia tries to get an app from apt.saurik.com, they will see a ”Host Unreachable” message or ”Refreshing Data” error message.
If you are a 3 subscriber, just dial 333 and tell the customer service representative to disable “adult content filter.”
If you are on China Unicom’s 3G subscribers with a jailbroken iPhone, can you confirm that Cydia is no longer accessible on your iPhone?