Whenever you install Joomla! on a server, you must take some measures in order to secure the installation.
Users often tend to leave the installation as it is, thus making the server vulnerable to hackers. That's why, when you install Joomla! on your server you need to change several configuration settings to avoid some major mistakes that will affect the overall site security.
Let's see the most common mistakes and why they are critical for your system:
Mistake #1. NOT TO download or upgrade to the latest Joomla! Version
New versions of Joomla! are released often with various security fixes and the developers are strongly recommending to upgrade to the latest version of Joomla!
It is important to download Joomla! packages from trusted sources or directly from joomla.org, otherwise you may compromise your system (you may download a modified package that could harm your website ). Periodical backups of the whole site are essential, providing a safety net in case something goes wrong caused by the update or some other unforeseen event. Already there are some specialized components that can create backups (files+database) very easily.