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Finance glossary

What is a man-in-the-middle (MITM) attack?

Bristol James
5 Min

A man-in-the-middle (MitM) attack occurs when a cyber attacker intercepts and relays messages between two parties who think they’re communicating directly. It’s a type of eavesdropping where the attacker controls the entire conversation without the knowledge of the parties involved.

MITM cyberattacks, sometimes referred to as monster-in-the-middle, machine-in-the-middle, or monkey-in-the-middle attacks, pose a significant online security risk as they allow attackers to seize and manipulate sensitive personal information, including login credentials, account details, and credit card numbers, in real time.

Understanding MITM attacks

A man-in-the-middle (MITM) attack occurs when an attacker secretly intercepts and possibly alters communications between two parties who believe they’re communicating directly with one another. The attacker inserts themselves between the two parties, relaying messages and controlling the entire conversation without their knowledge.

One example is active eavesdropping, where the attacker establishes independent connections with the victims and relays messages between them, making them think they’re communicating privately. The attacker must intercept and inject messages to maintain control. For instance, they could exploit an unencrypted Wi-Fi network as a point of entry.

The goal of an MITM attack is to bypass mutual authentication, and it can only succeed if the attacker convincingly impersonates each endpoint. For that reason, many cryptographic protocols incorporate endpoint authentication to prevent this kind of attack, such as trusted certificate authorities.

How do MITM attacks work?

In a man-in-the-middle (MITM) attack, cybercriminals insert themselves into data transactions or online communication, often through malware distribution. Attackers can intercept the data that users exchange during transactions or interactions by gaining access to their web browsers, particularly targeting secure authentication processes used in online banking and e-commerce sites.

These attacks typically involve two main steps: data interception and decryption. During data interception, the attacker intercepts data transfers between a client and a server, tricking both into believing they’re communicating directly with one another while the attacker acts as a proxy.

Here’s how it typically works:

  1. The attacker installs a packet sniffer to monitor insecure network traffic, such as users accessing HTTP-based websites or using non-secure public hotspots.
  2. Once a user logs into an insecure website, the attacker captures their information and redirects them to a fake website.
  3. The fake website replicates the original, gathering user data that the attacker can exploit to access the user’s resources on the legitimate site.

In the decryption phase, intercepted data is unencrypted, which allows the attacker to decipher and misuse it. This way, attackers engage in identity theft or disrupt business operations, using the stolen information for malicious purposes.

What are the types of MITM attacks?

Man-in-the-middle attacks come in different shapes and forms. Here are the main types of MITM attacks to be aware of:

  • Domain name system spoofing: Attackers manipulate domain names to redirect traffic to fake websites. Users may unknowingly land on malicious websites, believing they are accessing secure and trusted sites, leading to the theft of login credentials.
  • Internet protocol spoofing: Cybercriminals alter the source IP address of websites, email addresses, or devices to mask their identity. Users are deceived into interacting with a seemingly legitimate source, allowing sensitive information to be transferred to cybercriminals.
  • HTTP spoofing: In this attack, browser sessions are redirected to unsecured or HTTP-based websites without the user’s knowledge. Cybercriminals can monitor user interactions and steal personal information shared during these interactions.
  • Wi-Fi eavesdropping: Users on public Wi-Fi networks are tricked into connecting to malicious Wi-Fi networks and hotspots set up by cybercriminals. Fake Wi-Fi connections, often resembling nearby businesses, are used to intercept data.
  • Secure Sockets Layer (SSL) hijacking: SSL establishes encrypted connections between browsers and web servers. Cybercriminals intercept information traveling between the server and the user’s computer using another computer and a secure server.
  • Email hijacking: Attackers gain control of email accounts, including those of banks and financial institutions, to monitor user transactions. They may spoof legitimate email addresses to deceive users into transferring money to cybercriminals.
  • Session hijacking: Also known as stealing browser cookies, this attack involves cybercriminals stealing personal data and passwords stored in users’ browsing session cookies. They can gain access to confidential data, make purchases, or steal money from bank accounts.
  • Cache poisoning (ARP cache poisoning): This attack allows cybercriminals on the same subnet as victims to eavesdrop on all traffic routed between them. By poisoning the Address Resolution Protocol (ARP) cache, attackers redirect network traffic for malicious purposes.

How can I prevent MITM attacks?

Users can take several practical steps to prevent MITM attacks. Let’s go over some of them:

  • Use secure connections: Use websites with “HTTPS” in the URL bar and avoid unsecured public Wi-Fi connections. Also, it would be wise to implement multifactor authentication on your accounts for added security.
  • Beware of phishing emails: Be cautious of emails from unknown sources, especially those requesting login credentials or password updates. It’s important that you refrain from clicking on suspicious links and giving away personal information unless you’re 100% certain of the legitimacy of the message source.
  • Use Virtual Private Network (VPN) encryption: Encrypt internet connections and data transfers via VPNs, especially when using public Wi-Fi networks, like at a café or the library. VPNs provide an additional layer of security against potential MITM attacks.
  • Ensure endpoint security: Whenever possible, implement robust endpoint security measures, including antimalware and internet security products, to prevent malware on your devices.
  • Become acquainted with security standards: Learn about security standards and common cyberattacks to be able to identify malicious emails, implement VPNs, and take other security measures.

MITM attacks pose a significant threat to cybersecurity, as they allow cybercriminals to intercept and manipulate sensitive data exchanged between parties. However, by implementing proactive security measures and staying vigilant against common attack vectors, individuals and organizations can mitigate the risk of falling victim to these malicious activities.


  • Man-in-the-middle (MITM) attacks involve cybercriminals intercepting and manipulating data exchanged between parties.
  • Preventive measures include using secure connections (HTTPS), avoiding phishing emails, and encrypting data with VPNs.
  • Robust endpoint security and proactive security awareness are essential for safeguarding against MITM attacks.



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