Adversary-in-the-middle (AITM) attacks are an advanced form of cyber threat that intercepts communications between users and their intended digital destinations, often bypassing multi-factor authentication (MFA) systems to exploit vulnerabilities and launch complex phishing campaigns. These attacks, which have gained prominence since Microsoft’s 2023 warning, involve cybercriminals using techniques like reverse web proxies or browser-in-the-middle (BiTM) programs to manipulate user information and initiate multi-stage attacks, such as business email compromise (BEC). Best practices for defending against AITM attacks include implementing robust, phishing-resistant MFA protocols, utilizing conditional access policies to restrict access based on user identity and behavior, and continuously monitoring for threats to detect and mitigate potential attacks early. The attacks are especially dangerous as they can chain together with other cyberthreats, dynamically compromising sensitive data and leveraging interlinked vectors to target multiple accounts.