A "Man-in-the-Middle" (MitM) attack occurs when an unauthorized person intercepts communication between two parties, often without their knowledge. This attacker can eavesdrop, alter messages, or impersonate one of the parties, leading to data theft or manipulation. Common scenarios include unsecured Wi-Fi networks where attackers can easily access data being transmitted. To protect against MitM attacks, users should employ encryption methods, such as SSL/TLS, and avoid using public Wi-Fi for sensitive transactions. Additionally, being cautious about sharing personal information and verifying the authenticity of websites can help mitigate risks associated with these types of attacks.