Definition
Online security or 'cybersecurity' is a term used to describe a set of socio-technical practices which ensure the protection of sensitive information online. In this context, many security concerns can be mitigated by simply minimising the amount of personal information required in the first place; for example, evaluating whether it is necessary to store certain kinds of personally identifiable information such as names and addresses.
From a technical perspective, similarly to concerns around accessibility, effective security measures often simply involve implementing well-documented standards (such as those listed by MDN) or by using third-party tools that specialise in a given service (such as payments or data storage).
However, governance frameworks also has serious implications for security, and these are not so easily solved with technical knowledge but instead require clear guidelines within teams and between stakeholders. For example, it is important to make people aware of security risks before asking them to enter information into a system, even if that information seems benign.