Many websites are vulnerable to easily preventable defacements. There are various measures you can put in place to substantially reduce the risk of a defacement. The factsheet sets out the key characteristics of a defacement, what implications they have and what you can do to maximize your defence against such attacks.
Download the factsheet from here – https://www.ncsc.nl/english/services/expertise-advice/knowledge-sharing/factsheets/factsheet-help-my-website-has-been-defaced.html