Truly, completely securing a website is almost impossible; there are very many variables at play, from the security of the host to poor coding practices that leave vulnerabilities open to explicitly malicious coding introduced in plugins and themes.
You can however mitigate against as many possible website security vulnerabilities by installing specialist plugins that keep track of your website code- and file-changes and use their own updated database, much like an anti-virus application on your computer does, to check that no known hacking applications are running on the website. These also include intrusion-prevention features to stop malicious bots from trying to detect your admin login details through the use of brute-force attacks.
One such plugin, that we recommend to our WordPress clients, is WordFence (https://www.wordfence.com). This is a free to use plugin, with a premium version that unlocks more features, however the free version is enough for most websites.
The WordFence WordPress plugin can be found here – https://en-gb.wordpress.org/plugins/wordfence/ with a useful FAQ section covering installation and set up and any questions you might have regarding the security cover WordFence provides.
The best way, however, to help prevent malicious attacks on your website is to host it with a hosting company that takes website security seriously. Although such web host will be more expensive it’s worth the peace of mind knowing your brand is not going to be compromised.