Also I read here:
Apple releases new build of iOS 5.0.1 for iPhone 4S | The Verge
That iOS hacker MuscleNerd recently tweeted an unusual observation about the update: it's the first official 4S firmware with an accessible encryption key for the main file system, meaning you can browse the file system from a PC unimpeded. Lots of folks are pointing out that this means users will be able to get at Siri's files without committing piracy, and that could lead to a field day for Siri hacks. There's no official word from Apple at this point on exactly what's changed.
As well as this:
iPhone 4S displays 'No Service' or 'No SIM Card Installed' because it was updated for today and if you look at the bottom it mentions this new version of Ios 5.0.1.