In a man-in-the-middle (MITM) attack, the attacker inserts their machine between two hosts that are communicating with each other, and secretly relays and possibly alters the messages between them. The attacker can intercept, modify, or spoof the data, and the hosts are unaware that their communication is compromised. A MITM attack can target any communication channel that uses weak or no encryption, such as email, web, or wireless networks. A MITM attack can break the confidentiality, integrity, and authenticity of the communication, and can have various goals, such as eavesdropping, stealing credentials, impersonating a legitimate party, or redirecting traffic. A MITM attack can be prevented by using strong encryption protocols, such as TLS, IPSec, or SSH, and verifying the identity of the communication endpoints using certificates or other means. References: Implementing and Operating Cisco Security Core Technologies (SCOR) v1.0, Man-in-the-middle attack - Wikipedia, Man-in-the-Middle Attack: Types and Examples - Fortinet