This closely relates to the former post about privacy, hence my using of the same keywords. According to the Webster dictionary, security is a state where one is free from danger or threat, and has to be considered from a technical standpoint. Another great and lengthy definition was written down long ago on the highly reputable w3.org. This post will try to balance ease-of-use with security habits to keep and act upon, not some crypto-nerd phantasm. It will further assume that you set up a reasonably difficult password on your local computer when you installed it, and that you are starting fresh.
Difficulty: medium