If you have an iPhone and encountered a problem when trying to update or restoring your device called error 3194. This error is especially common if you are using Cydia. You can fix the problem by removing the Cydia SHSH caching server from your host file.
You can do this either by removing the Cydia IP address from your system host file manually or by using a program called TinyUmbrella (Windows / Mac).
After you open TinyUmbrella, click on the “Advanced” tab and uncheck where it says “Set Hosts To Cydia On Exit.” After you apply the changes, restart your computer. You should be able to update your iPhone to the new operating system now.