Jailbreak iOS 4.2 on iPhone 3GS using PwnageTool
Posted by Reshadat on September 16, 2010
PwnageTool has been updated by msft.guy to jailbreak iPhone 3GS on iOS 4.2(Old bootrom only). PwnageTool does hacktivation but is currently incompatible with Cydia. You’ll have to use OpenSSH to manually install Cydia applications.
You need to have an iPhone 3GS with old bootrom, jailbroken atleast...