The concept of an attack surface refers to the set of points where an attacker can try to enter, cause an effect on, or extract data from a system, environment, or asset. It is not static and increases with growth activities such as business transformation, cloud adoption, and mergers and acquisitions. Reducing the attack surface involves eliminating non-relevant assets, implementing basic security mechanisms, and prioritizing risk-based mitigation strategies. Attack surface management is crucial for organizations to secure what they don't know exists, protect their reputation, and demonstrate return on investment in security investments. Effective attack surface management platforms should provide real-time insight into the attack surface, prioritize discovered assets, include cloud monitoring capabilities, and combine with human-driven testing and stakeholder notification. The ROI of attack surface management can be assessed using the Return On Security Investment formula, which estimates annualized loss expectancy, mitigation ratio, and cost of solution to demonstrate security investment effectiveness.