What Is a Man-in-the-Middle (MITM) Attack? And How to Stop It

A man-in-the-middle (MITM) attack happens when a cybercriminal positions themselves between two parties to intercept and eavesdrop on private communications. They can then trick users into revealing sensitive data like passwords or banking credentials.

What Is a Man-in-the-Middle Attack?

Man-in-the-middle (MITM) attacks are a type of cyberattack in which a criminal intercepts data or conversations between two parties (like a user and an application or a client and a server). The attacker then alters or steals the data or impersonates one of the parties to convince the other that they are having an authentic interaction.

Cybercriminals use MITM attacks to access login credentials, payment information, and other sensitive data. It’s a common entry point for many costly cyberattacks.

These attacks are especially effective in environments where security standards like encryption and authentication aren’t present.

Learn how MITM attacks work, including the common techniques and real-world examples, and discover how to detect and prevent them.

How Does a Man-in-the-Middle Attack Work?

In MITM attacks, the attacker gets between the user and the application they are trying to access to successfully become the proxy. They point a gateway's IP address to their MAC address, so when a user makes a request, it's sent to the attacker instead of the gateway, routing all traffic through a proxy.

Here’s how MITM attacks work:

First, the attacker gains access to a vulnerable environment by connecting to or compromising a weak point in the communication path. Common targets include:

Public Wi-Fi Networks: Open, password-free networks let attackers easily join and intercept traffic.
Insecure Routers: Routers with default passwords or outdated firmware can be hijacked.
Phishing Emails: Victims may be tricked into installing malware that facilitates interception.
Hijacked Web Servers: Legitimate sites can be cloned or compromised to act as MITM proxies.

Next, the attacker positions themselves in the middle.

They use techniques like address resolution protocol (ARP) spoofing or domain name server (DNS) spoofing to impersonate a trusted part of the network, usually the router or server, so that traffic is redirected through their device.

The attacker then begins to intercept traffic. All data that the victim sends or receives now flows through the attacker’s system. This includes anything from browsing activity to sensitive login credentials.

If the data is encrypted (e.g., HTTPS), the attacker may decrypt the traffic.

Attackers use SSL stripping to downgrade the connection to HTTP, install fake certificates to break encryption, and use malware to read encrypted traffic locally.

After intercepting and decrypting the data, the attacker captures or manipulates the data.

Attackers can now steal information like usernames, passwords, credit card details, or inject malicious code into web pages the victim visits.

Finally, the attacker forwards the traffic to avoid detection

To keep the communication flowing and stay hidden, the attacker forwards requests and responses between the victim and the real destination, making the attack invisible to most users.

8 Common MITM Techniques

MITM attacks range from highly technical methods to taking advantage of human behavior through social engineering. Organizations should prepare for these possible attacks by implementing a multi-layered security approach, including technical safeguards and social engineering prevention.

Here are eight common MITM techniques that attackers use:

Address Resolution Protocol (ARP) Spoofing: Also known as ARP cache poisoning, this method tricks a computer into thinking the attacker's computer is the network gateway. The attacker accomplishes this by sending false information to the network to redirect connections.
Domain Name Server (DNS) Spoofing: Criminals can divert traffic from a legitimate site to a fake version by altering IP addresses in a DNS server. This can affect a large number of people because it involves hijacking a DNS server and altering records.
HTTPS Spoofing: Criminals obtain a spoofed domain name using non-ASCII characters that look similar to a legitimate website. Then, they register an SSL certificate to make the site look authentic.
Email Hijacking: Criminals compromise an email account using phishing scams and then commit other cyberattacks. An example is business email compromise (BEC), which utilizes social engineering and vendor impersonation to exploit trusted relationships.
Man-in-the-Browser: This method involves installing malware onto a person's device. This malware records the login credentials the user enters on websites. There are multiple ways to trick people into installing malware, but criminals can also accomplish this by finding browser vulnerabilities.
WiFi Eavesdropping: Public WiFi networks are vulnerable to eavesdropping. Criminals can compromise the network and monitor user activity, including login credentials and payment information. Alternatively, criminals may create a legitimate-looking public WiFi network to trick users into connecting.
SSL Hijacking: This method involves the criminal tricking the user and the application into thinking a session is secure when it's not a secure connection. The cyberattack is executed by forging SSL/TLS certificates between the two parties.
SSL Stripping: SSL stripping occurs when a criminal successfully convinces a browser to connect to an unencrypted version of a website (HTTP) instead of the encrypted site (HTTPS). This could expose sensitive information to the attacker.

How To Check for a Man-in-the-Middle Attack?

Man-in-the-Middle (MITM) attacks are difficult to detect because they exploit real-time data transfers and conversations. However, MITM attacks leave traces of indicators of compromise that users may see while browsing the web:

Severe latency when loading websites or using applications
Spoofed URLs, such as web5ite.com instead of website.com
Frequent and random disconnections
Absence of the "S" in the HTTPS connection in the web browser

Users should exercise caution when connecting to public or unsecured WiFi networks. Attackers can create or hijack these networks specifically to carry out MITM attacks. Once connected to a compromised network, criminals can monitor all transmitted data.

How To Prevent Man-in-the-Middle Attacks?

Prevention is essential to prevent a cyberattack from infiltrating your network or system. A multi-layered approach to security will give an organization a better defense system against cybercrimes like MITM attacks.

Fortunately, many tactics and tools exist to build a robust cybersecurity system. Some general tips include: