MitM attack - Security Software Glossary

What is a MitM attack?

A Man-in-the-Middle (MitM) attack occurs when an attacker intercepts and potentially alters the communication between two parties without their knowledge. The attacker positions themselves between the victim and the intended service, enabling them to eavesdrop on sensitive data like passwords or financial information, or inject malicious content into the communication.

Summary

MitM attacks exploit vulnerabilities in communication channels, where attackers intercept and manipulate data in real time. These attacks often involve stealing login credentials, payment data, or other personal information by impersonating a trusted entity. Common MitM types include Wi-Fi eavesdropping, HTTPS spoofing, and DNS hijacking. To detect these attacks, users should monitor for unusual activities like unexpected disconnections or invalid security certificates. Mitigation strategies include encryption (like TLS/SSL), VPNs, multi-factor authentication, and strict network security practices.

Deep dive

Types of MitM attacks

Wi-Fi eavesdropping: Attackers set up rogue Wi-Fi networks or access points with names mimicking legitimate ones (e.g., "Airport_WiFi"). When users connect, the attacker intercepts all transmitted data like login credentials or credit card numbers.
HTTPS spoofing: An attacker manipulates web traffic, leading victims to fraudulent websites with fake certificates that look legitimate. This compromises sensitive information entered into these sites like passwords or personal data.
DNS spoofing (hijacking): The attacker alters DNS query results, redirecting users to fake websites instead of the real ones. Since DNS translates human-readable domain names into IP addresses, altering these results misleads users to malicious sites designed to harvest credentials or distribute malware.
Session hijacking: The attacker steals cookies or session tokens, enabling unauthorized access to authenticated sessions, such as online banking or social media accounts.
Email interception: Intercepting emails in transit allows attackers to modify messages, rerouting payments or launching phishing attacks under the guise of trusted parties.

How MitM attacks work

An MitM attack usually involves two phases: data interception and decryption. This can look like redirecting users to fake websites and cracking encrypted data to steal credentials or disrupt operations. Here’s how attackers execute these attacks:

Interception

Attackers position themselves between two communicating parties (like a user and a service) to intercept, manipulate, or steal data. Common methods include:

Rogue Wi-Fi hotspots: Fake networks (e.g., “Free_Airport_WiFi”) capture user data.
Man-in-the-Browser (MitB): Malware alters secure browser sessions in real-time, targeting credentials or transactions.
Session hijacking: Attackers steal cookies to impersonate users in active sessions, such as online banking.
DNS spoofing: Users are redirected to malicious sites by manipulated DNS responses.
HTTPS spoofing: Attackers present fake SSL certificates, intercepting encrypted data under the guise of a secure connection.
Packet injection: Attackers alter packets mid-transit, inserting malicious code, often targeting IoT devices or insecure channels.
Proxy-based attacks: A proxy is placed between the user and server, secretly intercepting and modifying communication.

These techniques deceive both the user and server, making them believe they are communicating directly, leaving sensitive information exposed.

Accessing intercepted data

By accessing the intercepted data, attackers can access passwords, personal data, or financial information. They may manipulate this data for unauthorized transactions, identity theft, or other malicious activities by:

SSL stripping: Downgrading an HTTPS connection to HTTP.
SSL hijacking: Creating two independent SSL connections—one with the user and another with the service—without alerting the user.
Certificate forgery: Exploiting compromised certificates to avoid browser warnings.

How to stop MitM attacks

You can mitigate MitM attacks using layered defense to enhance organizational and individual security. Some of these strategies are:

VPNs for secure communication: Use Virtual Private Networks (VPNs) to encrypt internet traffic, especially on public Wi-Fi networks. Even if attackers intercept traffic, they won’t decipher encrypted data.
Network monitoring and IDS: Implement intrusion detection systems (IDS) to detect unusual network activity or anomalies like altered packets or IP spoofing attempts, signaling possible MitM attacks.
MFA (multifactor authentication): Adding an extra authentication layer helps prevent unauthorized access, even if credentials are compromised.
Encryption and HTTPS: Enforce SSL/TLS encryption and ensure HTTPS connections to secure data exchanges and prevent SSL stripping attacks.
Certificate pinning: Use certificate pinning to ensure communication only occurs with trusted servers, blocking impersonation attempts.
DNS security and ARP protection: Deploy DNSSEC (Domain Name System Security Extensions) to verify the integrity of DNS traffic and prevent DNS spoofing. Use static ARP (Address Resolution Protocol) entries to secure internal networks from ARP spoofing, which redirects traffic to malicious devices.
Regular audits and testing: Conduct penetration testing and security assessments to uncover vulnerabilities that may enable MitM attacks.
Public Wi-Fi precautions: Avoid entering sensitive information over public Wi-Fi without a VPN. Attackers often use fake hotspots to intercept traffic.
User awareness and phishing prevention: Educate users to recognize phishing emails and malicious links, common gateways for MitM attacks.

Signs of MitM attacks

Unusual or incorrect SSL warnings: Frequent browser alerts about invalid or mismatched certificates may indicate interception of HTTPS traffic.
Slower network performance: Unexpected slowdowns in connections could signal someone proxying traffic between users and websites.
Unauthorized login alerts: Notifications of account access from unfamiliar locations or devices might result from session hijacking.
Unexpected redirects: Being routed to suspicious websites despite entering valid URLs may indicate DNS or HTTP spoofing.
Duplicate public Wi-Fi networks: The presence of similarly named public Wi-Fi hotspots could be a sign of Wi-Fi eavesdropping attempts.
Session expiration or forced logouts: If you're logged out unexpectedly, an attacker might be attempting session hijacking.
Unusual app or browser behavior: Apps or browsers behaving abnormally or crashing could indicate tampering with communications.

Examples

UK rail station Wi-Fi attack: In September 2024, attackers redirected users to a webpage displaying prejudiced messages on the public Wi-Fi networks of 19 UK rail stations. Experts warned that such networks expose passengers' personal data to interception, especially without encryption or authentication controls. Following the breach, Network Rail disabled the Wi-Fi service, emphasizing the importance of personal hotspots and two-factor authentication (2FA) for public network security.
Gmail security alert for 2.5 billion users: In October 2024, a wave of AI-powered phishing attacks targeted Gmail users. Attackers simulated account recovery notifications and followed up with AI-generated phone calls mimicking Google support agents. They exploited legitimate-seeming elements like calls from numbers linked to Google business pages to manipulate users into providing account credentials. They also used Google Forms to craft convincing phishing emails, increasing the legitimacy of their attacks.
Google OAuth endpoint exploit: In early 2024, attackers exploited an undocumented Google OAuth endpoint, "MultiLogin," to maintain unauthorized access to user accounts even after password resets. Malware groups like Lumma and Rhadamanthys adopted this exploit by manipulating Chrome's authentication system to regenerate Google service cookies. The attackers also used encrypted tokens to avoid detection and bypass Google’s IP restrictions.

History

In the 1990s, attackers targeted unsecured communication protocols like Telnet and HTTP to intercept passwords and sensitive information transmitted over public networks. As online financial services became popular, MitM attacks evolved to session hijacking and SSL stripping, exploiting weaknesses in early encryption methods.

By the early 2010s, attackers shifted their focus to public Wi-Fi networks and mobile apps, using tools like packet sniffers to intercept data. High-profile breaches include the 2011 DigiNotar incident when a certificate authority was compromised to issue fraudulent certificates, and the Superfish adware scandal in 2015 which pre-installed software on Lenovo devices.

Future

MitM attacks will evolve with the growth of IoT, 5G networks, and cloud services, as these interconnected systems increase the attack surface. Attackers will target vulnerabilities in IoT devices, cloud APIs, and decentralized finance (DeFi) platforms. Emerging technologies like blockchain will see new MitM risks, especially as attackers attempt to intercept or manipulate cryptocurrency transactions.

AI and deepfake technologies will further enhance the sophistication of MitM attacks, automating phishing schemes and making detection harder. Regulations from GDPR and NIS 2 will drive organizations toward real-time monitoring and zero trust frameworks to counter these growing threats. As attackers innovate, proactively integrating AI-driven threat detection and behavioral analytics will be essential to stay ahead.

Man-in-the-middle attack (MitM)