Security is essential to gaining the trust of users. In our modern age, data breaches are very common and information security is very important. Users are starting to select products based on their security and privacy. Security is a huge field on its own, with many companies having their own security engineers and entire companies devoted to working as consultants to examine other companies' security practices. Security is the responsibility of everyone, just like monitoring, incident response, or UX. You should have experts on your staff to direct you, but you must not be ignorant about the topic and defer to your experts for everything.
When building software, or auditing technology for security matters, try thinking about the three following aspects of a piece of technology: