What Are MITM Attacks & How to Prevent Them
Man-in-the-middle (MITM) attacks continue to be a common cyberattack that companies and individuals face. It’s a broad category that includes disparate techniques employed with the same end goal in mind: intercepting information without being detected.
MITM attacks target communications of any kind and on any platform. Attackers seek gaps in network security and user awareness to solicit or steal information.
Understanding how to prevent MITM attacks or mitigate the risks start with understanding what they comprise and how they work. Ultimately, securing your authentication systems against MITM is the best defense.
What is a man-in-the-middle attack?
Man-in-the-middle (MITM) attacks are exploits in which a threat actor intercepts communications between two parties without either party noticing. Also called adversary-in-the-middle attacks, the objective in MITM attacks is to steal information – like users’ login credentials – by breaking authentication and gaining access to sensitive data or systems illegitimately.
Prominent examples of MITM attacks and related incidents in the past decade include:
In 2014, Lenovo’s Superfish adware scandal exposed millions to MITM vulnerabilities.
In 2015, Comcast used a MITM scheme to send copyright notices to unsuspecting users.
In 2017, Equifax’s infamous 147 million victim breach was partly due to MITM attacks.
The threat has been on the rise recently. Between Q1 2022 and Q1 2023, there was a 35% increase in the MITM attacks reaching victims’ inboxes.
Implications of MITM attacks
MITM attacks are dangerous because they allow attackers to steal information that lets them break authentication and access user accounts illegitimately. Worse yet, they often do so without detection, allowing insidious long-term access to your systems.
Once attackers have account access, they can compromise sensitive data. Stolen account numbers can lead to direct theft of employees’ or other users’ assets. In addition, threat actors can hold data hostage in a ransomware scheme, wherein they threaten to destroy or leak information unless victims pay a hefty sum.
Illegitimate access to information constitutes a compliance violation if the data in question is governed by regulations such as HIPAA, PCI-DSS, GDPR, etc. This can mean fines, criminal charges, seizure of service, and more. The immediate downtime and longer-term consequences of a data breach can lead to reputational damage and lost business from potential adopters of your app.
How MITM attacks work
MITM attacks vary widely in nature and work differently. Some are social engineering schemes that directly solicit victims' information, borrowing techniques from or fully incorporating phishing attacks. Others employ more technical measures to intercept information between unwitting parties without directly engaging with either.
Despite the variety, all MITM attacks comprise two basic stages: interception and decryption.
Interception: First, attackers intercept sensitive information exchanged between two parties. Attackers insert themselves between the parties by impersonating or seizing control over one or both accounts or some element of the platforms on which the parties communicate.
Decryption: Once attackers have the information, they must decrypt it. They render it usable by cracking encryption, soliciting or stealing more information, or otherwise breaking authentication further. All the while, they strive to avoid detection by all impacted parties.
MITM attacks are customizable to the specific individuals and accounts involved, the networks and devices used, and the information sought. Ultimately, they’re tough to predict.
Common types of man-in-the-middle attacks
Another element of MITM attacks’ variety and unpredictability is that these attacks utilize multiple methods for both interception and decryption. They’re also often paired with other attack vectors, like phishing, brute force, or DDoS attacks to maximize their chance of success.
However, most MITM attacks fall into one of the following archetypes:
Eavesdropping. Threat actors lure victims into unsecured WiFi networks disguised to look like trusted ones. From that position, they can intercept communications unnoticed.
Poisoning. Typically cache or Address Resolution Protocol (ARP) poisoning, these attacks leverage proximity within a subnetwork to intercept communications on it.
Highjacking. Attackers can also seize control of accounts by end users or would-be trusted institutions (i.e., their companies or banks) to solicit or steal data. Session hijacking is a common example, where attackers impersonate an authenticated user after stealing their session ID.
Spoofing. In DNS spoofing schemes, attackers alter the URL, domain name server (DNS), or other key information associated with a website. Victims then think they’re interacting with a legitimate website, but they’re unwittingly divulging information to the attacker.
These methods allow cybercriminals to intercept and decrypt information without being noticed, leading to direct theft, extortion, and other costly consequences.
How to detect MITM attacks
The first line of defense against MITM is a rigorous monitoring scheme that scans for, detects, identifies, and mitigates threats before they impact unsuspecting victims. From an institutional or development level, that means creating measures to identify the specific platforms on which users communicate.
You should monitor the networks devices connect to, and any contact with unidentified networks should be flagged as a potential threat. In addition, you should monitor the web locations users access, down to the spelling of the URL itself.
MITM attacks often leverage misspellings or other close similarities to make networks, URLs, and other locations appear safe. You can counteract this by prohibiting traffic with a deny-all-except policy that identifies or denies access to suspect areas.
Another focus for monitoring infrastructure should be the specific parties with whom people are communicating, along with the content and cadence of their communication. If an attacker spoofs or seizes control of a trusted account, their messages may differ from how the account owner typically speaks. Any irregularities could be an indicator of a MITM attack.
How to prevent MITM attacks
Detection is only half the battle – developers and adopters should also take proactive measures to prevent MITM attacks. This means reducing the likelihood of attempts, lowering the chances of reaching victims in case attempts are made, and minimizing the potential harm if they do manage to reach end users.
Preventive measures you should consider include (but are not limited to):
Secure communications. Since MITM is about intercepting communications, you should prioritize control over all channels people use to communicate. Monitor for and log all behaviors and connections to flag and address irregularities.
Encryption. Protect all communications and sensitive data with strong encryption so that, even if intercepted, information will not be readable or usable by cybercriminals.
Network security. Implement network monitoring, segmentation, and other controls to ensure users connect to only known, secure networks on all devices. On the app level, you can require a secure connection to specific networks to access certain data.
User awareness. Even the most secure systems rely on users’ security awareness to prevent attacks. Implement training as part of your onboarding process and at regular intervals.
You should also prioritize authorization and authentication. Controlling access to sensitive data and environments with secure auth methods adds an extra layer of security. So, even if MITM attackers steal information, they may be unable to break auth.
Secure authentication with Descope
Man-in-the-middle attacks are dangerous because of their flexibility and unpredictability. An attacker can tailor their approach to the network infrastructure, communication platforms, devices, or other factors specific to users of your app or website. Implementing proactive measures for monitoring, detecting, and preventing these threats is crucial.
One great place to start is identity and access management (IAM), which prioritizes secure authentication, user management, and authorization. You want a flexible system that makes logins easy without compromising security. Descope can help.