Quantifying the financial impact of IT security breaches

Internet security is a pervasive concern for all companies. However, developing the business case to support investments in IT security has been particularly challenging because of difficulties in precisely quantifying the economic impact of a breach. Previous studies have attempted to quantify the magnitude of losses resulting from a breach in IT security, but reliance on self‐reported company data has resulted in widely varying estimates of limited credibility. Employing an event study methodology, this study offers an alternative approach and more rigorous evaluation of breaches in IT security. This attempt has revealed several new perspectives concerning the market reaction to IT security breaches. A final component of the study is the extension of the analysis to incorporate eSecurity vendors and a fuller exploration of market reactions before and after the denial of service attacks of February 2000. The key takeaway for corporate IT decision makers is that IT security breaches are extremely costly, and that the stock market has already factored in some level of optimal IT security investment by companies.