Defense in depth is critical in combating phishing threats because no single security measure can provide complete protection against sophisticated attacks. By implementing multiple layers of defense, organizations can create overlapping security barriers that increase the complexity for attackers and reduce the likelihood of successful breaches. This approach includes not only technical solutions such as email filtering and malware detection but also emphasizes the importance of human vigilance. Trained staff serve as the final line of defense, equipped with the knowledge and skills to identify and respond to phishing attempts effectively.