Man-in-the-Middle Attacks (MitM): How Do They Work?

What is a Man-in-the-Middle (MitM) Attack?

 

A Man-in-the-Middle (MitM) attack is a cyberattack where a hacker secretly intercepts and manipulates communication between two unsuspecting parties. The attacker can eavesdrop on conversations, steal sensitive data, or even alter messages without the victims realising it.

The Goal of a Man-in-the-Middle Attack

 

Cybercriminals use MitM attacks for various malicious purposes, including:

 

• Stealing Sensitive Information - Attackers collect login credentials, credit card details, banking information, and personal data for identity theft, financial fraud, or sale on the dark web.
• Corporate Espionage - Businesses are prime targets as attackers intercept emails, contracts, or internal communications to gain competitive intelligence.
• Altering Transactions - Hackers modify payment details before the request reaches the bank, diverting funds to their own accounts.
• Spreading Malware - By injecting malicious content into a legitimate website, attackers trick victims into downloading malware or visiting fake login pages.
• Compromising Government and Military Communications - MitM attacks are commonly used in state-sponsored cyber espionage to intercept sensitive intelligence.

 

In short, the goal of a MitM attack is to profit from stolen data, disrupt operations, or manipulate victims without them realising it.

 

How a Man-in-the-Middle Attack Happens

 

A MitM attack unfolds in two main stages:

 

Stage 1: Interception – Gaining Access to the Communication

 

At this stage, the attacker inserts themselves between the two communicating parties without them knowing. To do this, they exploit vulnerabilities in networks, devices, or applications. Here are some common methods used to intercept traffic:

 

• Fake Wi-Fi Hotspots (Evil Twin Attacks) - An attacker sets up a rogue Wi-Fi network that appears legitimate (e.g., “Free Coffee Shop Wi-Fi”). When users connect, all their internet activity is routed through the hacker’s system, allowing them to capture sensitive information.
• ARP Spoofing (Local Network Hijacking) - In local network attacks, the attacker manipulates the Address Resolution Protocol (ARP) to trick devices into thinking the hacker’s system is the gateway to the internet. This allows them to intercept traffic meant for the real network.
• DNS Spoofing (Redirecting Users to Fake Sites) - By poisoning the Domain Name System (DNS) cache, attackers can redirect users to fake versions of websites (e.g., a fraudulent banking site) that steal login credentials.
• Session Hijacking - Attackers steal session cookies (which store authentication tokens) to gain unauthorised access to accounts without needing a password. This is common on unsecured Wi-Fi and poorly encrypted websites.
• SSL Stripping (Downgrading Encryption) - Most websites use HTTPS encryption to secure data transfer. However, hackers can force users to connect over unencrypted HTTP, making it easier to intercept and modify their traffic.

 

Stage 2: Decryption & Manipulation – Extracting or Altering the Data

 

Once the attacker has access to the communication, they can:

 

• Passively Eavesdrop - Monitor the conversation without making changes. This allows them to collect passwords, emails, banking details, and other confidential information.
• Actively Manipulate Data - Modify messages in real time. For example: Alter payment details in online transactions, inject malicious code into website traffic to install malware, and redirect users to phishing pages that look identical to real sites but steal login credentials.

 

Example of How an Attacker Modifies Data

 

Imagine a user logging into their online banking account. If an attacker is in the middle:

 

• The victim enters their login credentials and clicks "Submit".
• The attacker intercepts this request, steals the login details, and forwards the request to the real bank server.
• The bank authenticates the victim and sends a response.
• The attacker modifies the bank’s response, changing the account balance or adding a malicious link.
• The victim unknowingly interacts with the altered data, while the attacker takes control of their account in the background.

 

By operating in real time, MitM attackers can deceive both parties, making their presence extremely difficult to detect.

 

How to Detect a Man-in-the-Middle Attacks

 

MitM attacks are difficult to detect, but here are some warning signs:

 

• Unexpected SSL/TLS Warnings – If your browser warns you that a site’s security certificate is invalid, do not proceed. This could indicate SSL stripping.
• Frequent Disconnections from the Network – If your device keeps disconnecting and reconnecting to a network, an attacker might be trying to intercept traffic.
• Unusual Website Behaviour – If a familiar website looks slightly different or lacks HTTPS encryption, it may be a fake version created by an attacker.
• Slow Internet Speeds – If you notice laggy connections when entering sensitive data, an attacker may be intercepting and relaying your requests.
• Mismatched URLs – If a link redirects you to an unexpected domain, it could be a phishing attempt.
• Unexpected Pop-Ups Asking for Login Credentials – If you’re prompted to log in again when you shouldn’t be, someone might be trying to capture your credentials.

 

For businesses, using Intrusion Detection Systems (IDS) and network monitoring tools can help detect suspicious activities linked to MitM attacks.

 

The Role of HTTPS & the Padlock Symbol

 

Historically, the padlock symbol 🔒 in browsers indicated a secure HTTPS connection. However, Google has started removing it in Chrome, replacing it with a more neutral “tune” icon.

 

Many users misunderstood the padlock’s meaning—believing it signified a website was entirely safe, when in fact, HTTPS only ensures encryption and does not guarantee that a site is legitimate.

 

Users should focus on checking for HTTPS in the URL and be aware of browser security warnings. Attackers can still use SSL stripping techniques to force unencrypted connections, so being vigilant remains essential.

 

How to Prevent a Man-in-the-Middle Attack

 

Use Secure Networks

 

• Avoid Public Wi-Fi: If you must use it, always connect via a VPN (Virtual Private Network). Sensitive or private information such as banking should only be accessed through secure channels.
• Disable Auto-Connect to Wi-Fi Networks: This prevents your device from automatically connecting to rogue hotspots.
• Use Cellular Data for Sensitive Transactions: Mobile networks are harder to intercept than public Wi-Fi.

 

Strengthen Encryption & Security

 

• Always Check for HTTPS: Ensure websites use HTTPS, not HTTP. Look for "Secure" indicators in the browser.
• Use a VPN: A VPN encrypts all traffic, preventing attackers from intercepting data.
• Enable End-to-End Encryption: Messaging apps like WhatsApp and Signal offer secure communication.

 

Secure Your Devices

 

• Keep Your Software Updated: Regular updates fix security vulnerabilities.
• Use Strong, Unique Passwords: Avoid reusing passwords across different accounts.
• Enable Two-Factor Authentication (2FA): Even if an attacker steals your password, they won’t be able to access your account without a second verification step.
• Use Antivirus & Firewalls: Security software can detect suspicious activities.

 

MitM attacks are a growing cybersecurity threat, but with awareness and proper security measures, you can reduce your risk significantly. By using encrypted connections, avoiding suspicious networks, and staying vigilant for warning signs, you can keep your personal and business data safe.

 

Safeguard Your Organisation’s Data and Endpoints with Ensign

 

To combat today’s evolving threats, Ensign InfoSecurity offers comprehensive data protection and endpoint security solutions. Our advanced technologies provide real-time monitoring, encryption, and threat detection to safeguard both data in transit and at rest, while securing endpoints across your organisation. From detecting malware to blocking unauthorised access, Ensign helps organisations ensure the integrity and confidentiality of their critical data and systems.

 

Learn more about how Ensign’s data protection and endpoint security solutions here.