By what policy are SQL Server 2014 updates installed automatically?
You might be using Windows or Microsoft update on the server and that is set to Install updates automatically (recommended).
Windows Server Update Services (WSUS) enables administrators to manage the distribution of updates and hot-fixes released for Microsoft products to computers in a corporate environment.
You should change the setting to either

Check for updates but let me choose whether to download and install them
or

Never check for updates --&gt; This means that you own and are responsible for checking any updates, downloading them , testing and installing them on the box.


A good read - Stop Automatically Updating Production Servers