What is a Man-in-the-Middle (MitM) Attack? Definition, Examples, Prevention 

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

A man-in-the-middle (MitM) attack is a type of cyber attack where the attacker intercepts communications between two targets to steal confidential data. 

These attackers essentially “eavesdrop” on a conversation between two victims and collect sensitive or confidential data such as passwords, email addresses or financial details. They may also trick their victims into taking actions such as completing a transaction or transferring funds by altering the conversation without the hosts’ knowledge. 

While the meaning of MITM attacks is often to target individuals, they are still an area of concern for businesses and large organisations. 

One common point of entry for malicious actors is through SaaS applications such as messaging services and file storage systems. Attackers often deploy MITM attacks on organisations through these applications to gain access to an organisation's network and compromise key assets and infrastructure. 

Understanding Man in the Middle (MitM) attacks

Man-in-the-middle attacks are one of the oldest forms of cyber attacks. Cybersecurity experts have been looking for ways to protect people from intersecting communications since the 80s – but to no avail. 

In these sorts of attacks, the attacker secretly positions themselves between two communicating parties, whether this be two people or a person and a web application. They then intercept the information flowing between these two parties, allowing them to steal confidential or sensitive data. 

This attacker becomes an invisible conduit through which information travels, enabling them to listen to on sensitive conversations or manipulate the data being shared. 

Today, the majority of MitM attacks take place between an individual and a web application. Malicious actors exploit vulnerabilities in the communication channel, often on unsecured public Wi-Fi networks, compromised routers, or even through malicious software. 

Examples of Man in the Middle (MitM) MitM Attacks

While the basic concept of MitM is the same in most attacks, there are a number of different strategies attackers can use to initiate a MitM attack on their victim:

Rogue Access Point 

Devices equipped with wireless cards will often try to auto-connect to the access point that is emitting the strongest signal. Attackers can set up their own wireless access points and trick nearby devices to join their domain, allowing them to manipulate their victim's network traffic. 

his is dangerous because the attacker does not even have to be on a trusted network to do this – the attacker simply needs a close enough physical proximity to their victim. 

ARP Spoofing

ARP s used to resolve IP addresses to physical MAC (media access control) addresses in a local area network. When a host needs to talk to a host with a given IP address, it references the ARP cache to resolve the IP address to a MAC address. If the address is not known, a request is made asking for the MAC address of the device with the IP address.

An attacker wishing to pose as another host may respond to requests it should not be responding to with its own MAC address. With some precisely placed packets, they can intersect the private traffic between two hosts, taking valuable information such as the exchange of session tokens to gain full access to their application accounts. 

DNS Spoofing 

Similar to the way ARP resolves IP addresses to MAC addresses on a LAN, DNS resolves domain names to IP addresses. In DNS spoofing attacks, malicious actors attempt to introduce corrupt DNS cache information to a host in a bid to access another host using their domain name, such as www.onlinebanking.com. 

This leads to the victim sending sensitive information to a malicious host, who they believe is a trusted source. An attacker who has already spoofed an IP address will have a much easier time spoofing DNS simply by resolving the address of a DNS server to the attacker’s address.

mDNS Spoofing

Multicast DNS is very similar to DNS, but it’s done on a local area network (LAN) using broadcasts like ARP. This makes it an ideal target for spoofing attacks since people and devices can’t check the address of who they’re communicating. Devices such as TVs, printers, and entertainment systems make use of this protocol since they are typically on trusted networks. 

When an app needs to know the address of a certain device, such as tv.local, an attacker can easily respond to that request with fake data, instructing it to resolve to an address it has control over the victim will then see the attacker’s device as trusted for a duration of time.

Identifying Man in the Middle (MitM) attacks

Identifying a man-in-the-middle attack can be difficult without taking the proper steps. If you’re not actively looking for signs that your communications have been intercepted, an MITM attack could go unnoticed until it is too late.

The main way to identify a possible MITM attack is to check for proper page authentication and implement some sort of tamper detection. However, this requires additional forensic analysis after the fact.

How to prevent Man in the Middle (MitM) attacks

While identifying man-in-the-middle attacks is important, It is better to take preventive measures to stop MITM attacks before they happen. Being aware of your browsing habits and recognising potentially dangerous areas can be essential for keeping your network secure. 

Here are five of the best practices to prevent MITM attacks from compromising your communications:

1. Use HTTPS. HTTPS is a secure protocol that encrypts your communications, making it much more difficult for attackers to intercept them. Most websites now use HTTPS, but you can always check the URL bar of your browser to make sure. If the URL starts with "https://," then the site is using HTTPS.
    
2. Avoid public Wi-Fi. Public Wi-Fi networks are often unsecured, making them easy targets for MITM attackers. If you must use public Wi-Fi, be sure to connect to a reputable network and use a VPN.
    
3. Keep your software up to date. Software updates often include security patches that can help protect you from MITM attacks. Make sure to install software updates as soon as they are available.
    
4. Use a firewall. A firewall can help block unauthorized traffic from reaching your computer. This can help protect you from MITM attacks as well as other types of cyberattacks.
    
5. Be careful what links you click on. Attackers often send phishing emails or text messages that contain links to malicious websites. If you click on one of these links, you could be infected with malware that could be used to launch an MITM attack. Be sure to only click on links from trusted sources.

Final thoughts

Man-in-the-middle attacks are a powerful weapon in cybercriminals’ arsenal, capable of undermining the security of digital communications and potentially leading to financial and personal losses. 

Understanding the mechanics behind these attacks is the first step toward effective prevention. In the world of cybersecurity, knowledge and proactive defence are key to safeguarding sensitive information and protecting yourself from these sorts of threats.