Exploring the Materiality of Data Breach Disclosures on the Australian Stock Exchange

This study examines Australian Stock Exchange (ASX) data breach announcements to provide insights into the extent and nature of data breach disclosures, as well as the costs, particularly to stakeholder relationships. Using a dataset of all data breach‐related announcements on the ASX, we identify a lack of data breach disclosure and, where disclosures are made, a notable absence of detail. To examine how the concept of materiality is applied, given its role as a threshold for disclosure to stock markets globally, we provide an in‐depth examination of the case of Landmark White (LMW), the only company to disclose a material impact from its data breaches to the ASX. We identify an announcement paradox, where the data breach at LMW became material over time as stakeholders reacted to the announcements, pointing to a contagion effect. We recommend the creation of likely‐market‐effect models, which allow companies to calculate the likely share price impact of a data breach and use this in their decision to disclose. This approach represents a simple first step in reconceptualizing continuous disclosure regimes for the digital age, aimed at enhancing the transparency and reporting of cyber incidents to stock markets globally.