What is MITM?

Man-in-the-middle (MITM) is a type of cyber attack where a bad actor secretly sits between two people or devices that are trying to talk to each other. The attacker can listen to, copy, or even change the messages without either side knowing.

Let's break it down

  • Man: the attacker, a person or program that wants to interfere.
  • In the middle: positioned between the two legitimate parties, like a hidden relay.
  • Attack: an intentional act to cause harm or steal information.
  • Intercept: catching the data as it travels from one side to the other.
  • Alter: changing the content of the data (e.g., swapping a bank account number).
  • Communication: any exchange of data - emails, web pages, messages, etc.
  • Two parties: the sender and the receiver who think they are talking directly.

Why does it matter?

If a MITM attack succeeds, personal passwords, credit-card numbers, or confidential business data can be stolen or tampered with. It undermines trust in online services and can lead to financial loss, identity theft, or damage to a company’s reputation.

Where is it used?

  • Public Wi-Fi hotspots where attackers set up rogue access points to capture traffic.
  • Compromised routers or ISP equipment that silently forward and modify users’ web requests.
  • Malicious browser extensions that intercept and rewrite web pages you visit.
  • Corporate network breaches where an intruder inserts themselves between internal systems and the internet.

Good things about it

  • Highlights weaknesses in unencrypted connections, prompting stronger security standards.
  • Drives the adoption of HTTPS, TLS, and end-to-end encryption across the web.
  • Helps security professionals develop detection tools and monitoring techniques.
  • Encourages developers to implement certificate pinning and mutual authentication.
  • Raises public awareness about safe browsing habits and the risks of open Wi-Fi.

Not-so-good things

  • MITM attacks can be very hard to detect, especially when the attacker mimics legitimate servers.
  • Successful attacks can lead to severe financial loss, identity theft, or corporate espionage.
  • Defending against them often requires complex infrastructure (e.g., certificate management, VPNs).
  • Attackers need a certain level of technical skill, making the threat persistent and evolving.