Man-in-the-Middle Attack

A man-in-the-middle (MITM) attack is a form of cyberattack where the attacker secretly relays and possibly alters communications between two parties who believe they are directly communicating with each other. 

MITM attacks allow attackers to intercept, send and receive data meant for someone else, potentially without either party knowing their communication has been compromised.

MITM attacks are a significant threat to organizations and individuals because they can allow attackers to steal sensitive information like login credentials or financial data. Defending against them is an important part of cybersecurity.

Key Concepts

Definition

A man-in-the-middle attack involves three parties: the two intended communicants and the attacker. The attacker intercepts communication between the two parties and can observe or even modify the traffic before relaying it on to the intended recipient. The two communicants believe they are directly communicating when in fact the entire conversation is being controlled by the attacker.

Purpose

MITM attacks aim to secretly intercept communication, enabling the attacker to gain unauthorized access to sensitive information. The primary purposes are:

• Eavesdropping - The attacker can passively monitor the communications and gain insider knowledge. This compromised data could include usernames, passwords, PIN numbers, financial information, trade secrets, or other sensitive material.
• Hijacking - The attacker can actively insert themselves into the communication stream, impersonating each end for their own gain. For example, logging into a compromised account or making transactions.
• Tampering - The data flow can be altered or replaced to inflict some kind of damage. For example, changing bank transfer details or planting false information.
• Re-routing - Communication can be redirected to a different destination of the attacker's choice. For example, redirecting a browser to a malicious site.

Relevance

MITM attacks exploit the inherent trust relationships that exist between two communicating parties. As long as the attacker can successfully impersonate each end and relay the intercepted data fast enough to avoid detection, neither party will be aware their communication has been compromised.

This makes MITM a powerful attack vector relevant to many different environments:

• Remote access via public networks – the online services we use daily often transmit sensitive data that could be intercepted over the public internet.
• Wireless networks – technologies like WiFi and Bluetooth rely on radio transmission, which is more easily intercepted than wired networks.
• Supply chain – an attacker can compromise hardware or software components that end up as part of a trusted system.
• Cryptographic flaws – weaknesses in encryption algorithms or improper implementation can sometimes be exploited.

Also Known As

• Manipulator-in-the-middle
• Adversary-in-the-Middle
• Fire brigade attack
• Hole in the wall attack
• Bucket brigade attack
• Meet in the middle attack
• Janus attack

Components/Types

There are two main components in any MITM attack: interception and relaying. Beyond that, MITM attacks can take on many forms depending on how these steps are executed. Some examples include:

ARP Spoofing

A common MITM technique on local networks using the ARP protocol. The attacker sends falsified ARP messages to each victim, associating the attacker's MAC address with the IP address of the other victim. Traffic subsequently gets intercepted and relayed by the attacker rather than directly between endpoints.

SSL Stripping

Many websites use HTTPS encryption to secure data in transit. SSL stripping involves intercepting traffic and forcing communication over plain unencrypted HTTP instead of HTTPS, allowing data to be read or altered before relaying it on to victims.

Wi-Fi Evil Twin

Wireless MITM attack where the attacker mimics a legitimate Wi-Fi access point. Connecting victims route their traffic through the fake access point, allowing the attacker to intercept communications.

BGP Hijacking

Intercepting internet traffic at scale by exploiting the Border Gateway Protocol which controls traffic routing between internet network operators. The attacker impersonates victim networks to re-route traffic through themselves for interception.

Supply Chain Attack

Compromising hardware or software components before they are installed as part of a trusted system. Allows an attacker to subsequently intercept communications on the target network or system.

Quantum MITM Attack

A theoretical attack on secure quantum key distribution by intercepting and manipulating entangled particle transmission. As quantum computing matures, this emerging cryptographic threat warrants attention.

Importance in Cybersecurity

MITM attacks pose a serious cybersecurity threat:

Security Risks

• Data breach – interception can expose sensitive data like passwords, messages, financial details etc.
• Identity theft – credentials harvested can allow the attacker to impersonate users and access their accounts.
• Manipulation – attackers can alter intercepted data to inflict damage before relaying it.
• System compromise – footholds gained via MITM can be used to pivot deeper into a target network.

Mitigation Strategies

• Encryption – use of cryptographic protocols like TLS prevents data being read or modified during MITM.
• Authentication – requiring cryptographic authentication for sensitive transactions can detect tampering or impersonation.
• Endpoint security – firewalls, antimalware and intrusion prevention systems help block and detect MITM activities.
• Monitoring – solutions like Security Information and Event Management (SIEM) can identify potential MITM behavior.
• User education – training staff to identify signs of MITM attacks like invalid certificates.

Best Practices

Organizations should take a layered defense approach to protecting against MITM and related threats:

• Utilize encryption like HTTPS wherever sensitive data is transmitted.
• Only use trusted networks or VPNs when accessing services remotely - avoid public Wi-Fi.
• Verify the authenticity of hardware and software used in critical systems to prevent supply chain tampering.
• Keep firewalls, antivirus and intrusion detection solutions up-to-date to block known threats.
• Employ stringent access controls and monitoring to help identify any abnormal activities across networks that could indicate an attack.
• Educate staff on spotting signs of tampering like invalid certificates and encourage reporting of suspicious network activity.

Related Terms

• Phishing - Social engineering scheme where victims are duped into sharing credentials or sensitive data.
• Evil Twin - Fake wireless access point impersonating a legitimate one to intercept connected victims' traffic.
• Session Hijacking - Taking control of an existing user session like a compromised login.
• Spoofing - Falsifying data to masquerade as a trusted source.

References

• OWASP: www.owasp.org/www-community/attacks/Man-in-the-middle_attack
• MITRE ATT&CK: attack.mitre.org/techniques/T1557/
• CISA Alert TA18-074A: www.cisa.gov/uscert/ncas/alerts/TA18-074A

Man-in-the-middle attacks pose a serious threat any time sensitive information is transmitted over networks. Attackers can intercept communications between two trusting parties to steal or manipulate data. Encryption, authentication and layered security controls are key to guarding against MITM threats. But cybersecurity awareness among staff is equally important, as simple social engineering techniques are often used to initiate MITM scenarios. With the right mix of technical defenses and informed users, organizations can reduce their exposure and frustrate these kinds of pervasive attacks.