The recent NTP (network time protocol) security update from Apple was the first that Apple silently pushed to users, updating their systems without first notifying them of an available update and then requiring users specifically go to the App Store to install it; however, while intended for swiftly updating supported versions of OS X, this does not patch versions of OS X that are no longer supported by Apple.
This automatic approach was taken for the NTP update for several reasons. For one, it simply required a small file change and a re-launch of a background process, so there was no need to interrupt users in the middle of their work. In addition, the network time daemon is an essential part of an operating system’s security, since proper time synchronization between your Mac and other servers is required to establish some encrypted connections.
The update, which simply replaces the ntpd daemon (the program that runs in the background), will have replaced the file with the following versions on Apple’s supported OS X platforms, and fixes the critical flaw that allows for arbitrary code execution in the OS: