In IT security, a man-in-the-middle attack (MITM), also known as a hijack attack is an attack where the attacker secretly relays and possibly alters the communications between two parties who believe that they are directly communicating with each other. Attackers might use MitM attacks to steal login credentials or personal information, spy on the victim, or sabotage communications or corrupt data.

Man-in-the-middle attacks come in two forms, one that involves physical proximity to the intended target, and another that involves malicious software, or malware. One example of a MITM attack is active eavesdropping, in which the attacker makes independent connections with the victims and relays messages between them to make them believe they are talking directly to each other over a private connection, when in fact the entire conversation is controlled by the attacker. A hacker can be in physical proximity or within the reception range of an unencrypted Wifi access point making it easier to insert themselves as a man-in-the-middle. Although encryption can be used to help prevent against MitM attacks, threat actors will often reroute traffic to fraudulent phishing sites or simply pass on traffic to its intended destination once harvested or recorded - making detecting these attacks extremely difficult.

MTIM attcks are not as prevalent as ransomware or phishing attacks, but they are an ever-present threat for organizations. MITM attacks can be prevented or detected by two means: authentication and tamper detection. Authentication provides some degree of certainty that a given message has come from a legitimate source. Tamper detection merely shows evidence that a message may have been altered. Guardian Digital protects clients against MitM and other complex exploits, implementing advanced email authentication to its fullest and safeguarding against phishing and fraud with multiple layers of purpose-driven security including real-time URL scanning and broad-type file analysis.