There are so many reasons web pages are hacked. However, this article will explain a quick overview on what are the common techniques used by hackers to hack into your site.
For example, using a simple command can target not just one but many sites that are hosted under the same server. Hackers will need additional information about your website like:
Web Server specifications
Your name, address, phone, etc.
Scripts used in your site,
Server operating system
Your Server open ports.
Here is an infographic about WordPress security that is roughly the same even on non-wordpress sites.
Read the rest of the story here:Â http://resources.infosecinstitute.com/hacking-a-wordpress-site/