You've probably only just got around to updating your iPhone, iPod touch, or iPad to iOS 4.3.4 and along comes another security update released by Apple to protect your iDevice.
The new update, which will be triggered when you next plug in your Apple product to iTunes, fixes yet more security holes found in the mobile operating system and is recommended for all users (well probably not those who like to Jailbreak them).
The 614.9MB download comes just 10 days after Apple issued iOS 4.3.4, and according to the Apple knowledge base page on the matter is designed to stop an attacker with a privileged network position capturing or modifying data in sessions protected by SSL/TLS. Scary.
The update is available now.