Currently, many powerful applications designed to combat social deviations are available, like the web-filtering systems, which measure the content of a website before submitting it to the user, notifying whether the content of the website presents (or not) information related to pornography, violence, racism, among others, and prompting the user to not accessing the site, or even blocking access to the website. Nevertheless, frequently the feedback of these systems is not well-designed, which may confuse users and lead to mistakes, disappointments, and misunderstandings. In order to reduce this concern, a method is provided to developers with guidance in designing usable security notifications to be incorporated in web-filtering systems. The method is structured through a library of user interface design patterns which integrates essential concepts of security and usability. The authors show the effectiveness of the patterns by using an illustrative example as a proof-of-concept together with a preliminary study.