Unattended-upgrades can download and install security upgrades automatically and unattended, taking care to only install packages from the configured APT source, and checking for dpkg prompts about configuration file changes. Apticron is a simple script which sends emails about pending package updates such as security updates, properly handling packages on hold both by dselect and aptitude.
Found errors? Think you can improve this documentation? Simply click the Edit link at the top of the page, and then the icon on Github to suggest changes.