1. Security Theme
2. Vulnerability on your computer
3. Vulnerability on WordPress
4. Web server vulnerability
5. Network Vulnerability
Before, more discussing about these components let me tell you what is Security? “Fundamentally, security is not about perfectly secure systems. Such a thing might well be impractical, or impossible to find and/or maintain. A secure server protects the privacy, integrity, and availability of the resources under the server administrator's control.”
Security Theme is nothing more than general ideas while considering security for each aspect of your system. You can secure your system in three aspects such as Limiting access, Containment and Preparation and knowledge.
a) Limiting access: Making smart choices that reduce possible entry points available to a malicious person.
b) Containment: Your system should be configured to minimize the amount of damage that can be done in the event that it is compromised.
c) Preparation and knowledge: Keeping backups and knowing the state of your WordPress installation at regular intervals. Having a plan to backup and recovery your installation in the case of catastrophe can help you get back online faster in the case of a problem.
Vulnerability on your computer:
Make sure the computers you use are free of spyware, malware, and virus infections. No amount of security in WordPress or on your web server will make the slightest difference if there is a key logger on your computer.
Always keep your operating system and the software on it, especially your web browser, up to date to protect you from security vulnerabilities.
Vulnerability on WordPress:
Like many modern software packages, WordPress is updated regularly to address new security issues that may arise. Improving software security is always an ongoing concern, and to that end you should always keep up to date with the latest version of WordPress.
While your WordPress software is updating then there confirmed that no security issues (like vulnerable file, viruses, malware etc.) is downloaded with it. If you think you have found a security flaw in WordPress, you can help by reporting the issue in FAQ’s of WordPress site.
Web Server Vulnerability:
The web server running WordPress, and the software on it, can have vulnerabilities. Therefore, make sure you are running secure, stable versions of your web server and the software on it, or make sure you are using a trusted host that takes care of these things for you.
If you're on a shared server and a website on the same server is compromised, your website can potentially be compromised too even if you follow everything in this guide. Be sure to ask your web host what security precautions they take.
The network on both ends WordPress server side and the client network side should be trusted. That means updating firewall rules on your home router and being careful about what networks you work from. An Internet cafe where you are sending passwords over an unencrypted connection, wireless etc is not a trusted network.
Your web host should be making sure that their network is not compromised by attackers, and you should do the same. Network vulnerabilities can allow passwords and other sensitive information to be intercepted.