The Impact of Cyber‐Attacks on the Stock Prices, Bid‐Ask Spreads and Trading Volume of Target Firms: Australian Evidence

ABSTRACT We examine announcements of cyber‐breaches by firms listed on the Australian Securities Exchange to assess price and liquidity effects under Australia's continuous disclosure regime. Using an event study method, we find cumulative abnormal returns of −8.4% over a −30 to +30 day window, preceded by information leakage and followed by persistently wider bid–ask spreads and elevated trading volumes. Impacts are stronger when breaches involve financial loss and are smaller for firms in the ASX 100 Index. Many breaches are first reported via mainstream media rather than through the Australian Securities Exchange, raising compliance concerns with listing rules. Our findings provide guidance for boards, regulators, and investors on the pricing of cyber risk and continuous disclosure obligations.