What Is a Man-in-the-Middle Attack?
Cyberattack cases are rising, and it’s easy to see why. Attackers are always watching your every move to obtain all that seems uncrackable, particularly your personal information. Man-in-the-middle (MitM) attacks are just one example. In this article, learn what a man-in-the-middle attack is, how they work, and how to prevent them.
What is a man-in-the-middle (MitM) attack?
A man-in-the-middle attack (MitM attack) is a form of cyber threat in which an attacker secretly intercepts and possibly alters the communication between parties. For instance, a threat actor can position themselves between a user and a website that believes they communicate directly.
The user assumes they're interacting exclusively with a trusted system during all this time. Because of that, they willingly relinquish login details, payment information, or any sensitive data being transmitted.
Often, cybercriminals set up a lookalike WiFi network that appears legitimate or hack an existing network. When you connect, attackers access all the data passing through the network. The goal is to catch the data meant for someone else.
A MitM attack aims to eavesdrop on the data being exchanged. An attacker can also modify the content of the message or remove it altogether. Alternatively, they could impersonate one or both parties to send false information.
MitM cyberattacks are insidious threats to online interactions. People with bad intentions use them as an initial gateway to potentially alter conversations.
Note that this type of cyberattack can occur in any form of online communication, from email and web browsing to social media. However, sophisticated MitM attacks are very tactical. It’s notoriously difficult to track, trace, and subsequently stop before they steal data.
Nonetheless, this attack vector does have some subtle signs, including landing on a suspicious link on a website. Bad actors also prefer to launch these attacks through free public WiFi networks. Therefore, users should pay attention to their online environment at all times.
How does a man-in-the-middle attack work?
In a MitM attack, threat actors place themselves in the "middle" of data transfer. Once they are in, the attackers interrupt the conversation while also sending malicious links to participants in a way that might not be detected until it is too late.
A successful MitM attack has two main phases: data interception and decryption. The interception phase involves an attacker intercepting data flowing between the client, like your computer, and the server, which is the website you're trying to communicate with.
The attacker then tricks both the participants into believing that they are communicating securely with each other. This is accomplished through various methods, such as DNS spoofing. To avoid raising suspicion, the attacker establishes a connection to the real server on behalf of the client. The attacker then acts as an invisible intermediary or proxy, relaying the data between them.

Steps to man-in-the-middle data interception
Let’s break down the steps in the data interception stage:
- Installing a packet sniffer. A packet sniffer is a software program that captures data packets flowing across a network. In this case, the attacker uses it to identify unencrypted traffic (like HTTP) that can be easily intercepted.
- Information retrieval. Once a vulnerable user logs in to an insecure website, the attacker can potentially steal their login credentials transmitted in plaintext.
- Redirecting data to a fake website. The attacker has the user's login credentials ready. Next, this information will be used to redirect the user to a fake website. Such websites are designed to mimic the appearance of the original website that the user was trying to access.
After interception, the information must be decrypted to be useful to the attacker. This should be done without the user, the application, or the service provider’s knowledge.
This step is crucial for the attacker because it transforms the captured encrypted data into a usable format. With the now decrypted data, the attacker can use it to conduct malicious activities.
How is a MitM attack launched?
Performing any attacks on computer networks required distinct steps. But MitM attacks often start with:
- Compromised networks. Unauthorized persons gain access to a network, either through distributing malware or exploiting vulnerabilities.
- Insecure access points. Cybercriminals will set up a rogue WiFi hotspot and make it free to the public, luring them to connect to them. They also use malicious network devices.
- Poor router security. Routers set to default passwords or not updated are susceptible to hacking.
- Phishing emails. You might download malware by clicking fake links or attachments on a website, application, or email.
Most attacks are executed on public WiFi networks because they are more vulnerable to cyber threats than private home or office networks. This vulnerability results from several factors, including a lack of encryption and authentication and their shared nature.
These networks are usually designed to be accessible to anyone within its range. Free WiFi networks are often installed for convenience in places like cafes, airports, and hotels.
Home and office networks are more protected, and only authorized people can connect to them.
What are the different types of MitM attacks?
There are several types of man-in-the-middle attacks, each exploiting different vulnerabilities to achieve similar goals. These passive attacks can manifest in several forms, including:
- WiFi eavesdropping. Attackers create fake WiFi hotspots with compromised legitimate hotspots. When users connect, the attacker hijacks their network traffic and steals login credentials, emails, and other sensitive information.
- DNS spoofing. DNS spoofing is a man-in-the-middle attack in which malicious actors manipulate the domain name system (DNS) to redirect users from legitimate websites to fake ones designed to infect devices with malware.
- ARP spoofing. This attack exploits the Address Resolution Protocol (ARP) used by devices on a network to communicate. The attacker impersonates another device's IP address, tricking other devices on the network into sending their traffic through the attacker's machine.
- SSL (Secure Sockets Layer) stripping. In this attack, the criminal downgrades a secure HTTPS connection to an insecure HTTP connection, allowing them to intercept the unencrypted data exchange between the user and the server.
- SSL hijacking. This advanced MitM attack involves stealing a user's existing secure session with a website. The attacker then impersonates the user and gains unauthorized access to their account.
- Email hijacking. Attackers gain access to a victim's email account and intercept or tamper with emails. They can then use this access to launch further attacks or change supposedly confidential conversations.
- Session hijacking. Online thieves stealthily take over your digital session without you noticing. This attack targets the session cookies used by websites to identify logged-in users. Once stolen, these cookies allow the attacker to impersonate the victim and access their account.
- Man in the browser (MitB). This attack involves injecting malicious code into a user's web browser. This code can then steal data entered into websites, redirect users to phishing sites, or inject fake content into web pages.
At what layer do MitM attacks occur?
MitM attacks can occur in different layers of the OSI model, a conceptual framework for networking communication. This, however, depends on the specific techniques an attacker employs.
Attacks like session hijacking and some phishing attempts target the application layer. They exploit vulnerabilities in specific applications to steal session cookies.
DNS spoofing attacks occur at the network layer. By tampering with DNS records, the attacker redirects users from legitimate websites to fake ones.
In the data link layer, threats like ARP spoofing manipulate how devices communicate on a network. The attacker impersonates another device's MAC address, tricking other devices into sending their traffic through the attacker's machine.
Other types of MitM attacks, like SSL stripping, occur in the transport layer. The attacker downgrades a secure HTTPS connection to an insecure HTTP connection, allowing them to intercept the unencrypted data exchange.
What makes MitM attacks dangerous?
MitM attacks are dangerous for several reasons. They can lead to identity theft and financial fraud; the attacker can use login credentials, personal information, or session cookies to damage a victim's reputation or hack financial accounts. Furthermore, they violate privacy. Attackers can compromise the privacy of online communications, which can be used for blackmail or harassment.
Data manipulation is also an issue; in some MitM attacks, attackers interfere with messages in transit rather than simply stealing the data. Man-in-the-middle attacks also disrupt business operations, capturing login credentials and gaining the ability to harm operations and data security.
As people become aware of MitM attacks, attackers continuously develop new methods to remain undetected. Therefore, you must be more vigilant about avoiding falling victim to attacks.
How to prevent man-in-the-middle attacks
Mitigating MITM attacks involves layering defenses, understanding vulnerabilities, and practicing good digital hygiene. Here are some ways you or organizations can protect themselves and prevent MitM attacks.
- Use secure HTTPS connections. Ensure that your online interactions occur over HTTPS, which encrypts data as it travels across the web. Look for the padlock symbol in your browser to verify a secure connection.
- Be cautious of phishing emails. Exercise skepticism and scrutiny when opening emails, especially those with suspicious offers, unsolicited password reset links, or urgent requests.
- Use a virtual private network (VPN). A VPN encrypts your data stream whether you're using public WiFi or a private network.
- Implement endpoint security. Use firewalls, antivirus software, and other tools to combat malware. Regularly update your software to patch vulnerabilities.
- Embrace multifactor authentication (MFA). Organizations can enhance security by requiring additional proof beyond a simple password, such as biometrics or tokens.
- Employ digital certificates. Be sure to verify website certificates to validate their authenticity.
- Avoid public WiFi. Though free, public networks are insecure. If you have to connect to them, use a VPN or proxy.
Frequently asked questions
What should I do if I suspect a MitM attack?
Act immediately. You can disconnect the WiFi to prevent further exposure, change your login credentials for all your accounts, or scan the malware using the right tool. Finally, you can report to the appropriate authorities.
Is MitM a widespread threat?
Yes, MitM attacks remain a serious concern in the cybersecurity landscape. They are growing in sophistication and size. Therefore, you must remain aware and take action to prevent them.
What is a real-world example of a MitM attack?
Lenovo's 2015 Superfish adware incident is a good example. Lenovo laptops arrived with pre-installed Superfish adware, which then injected advertisements into users' encrypted web traffic and made user data vulnerable to prying eyes.