You can know jailbreak an 4.3.1 iOS device. This does not work on the iPad 2 and lower iPods/iPhones. The jailbreak is with Redsn0w so you will loose all your stuff(jailbreak apps like MxTube) which you don’t have in iTunes. Hopefully Greenpois0n will be out soon if you don’t want to loose your stuff.

Watch below for how to jailbreak 4.3.1: