What is a man in the middle attack?
A man in the middle (MITM) attack is a sophisticated type of cyber attack where a malicious actor intercepts communication between two parties without their knowledge. This type of attack can occur in any form of online communication, such as email exchanges, web browsing, and any other data transfer. The attacker positions themselves “in the middle,” allowing them to eavesdrop, manipulate data, or impersonate one of the parties to gain unauthorized access to sensitive information.
Man in the middle attacks pose serious threats to both individuals and organizations. They can lead to financial loss, data breaches, reputational damage, and even legal implications if sensitive customer data is compromised.
How MITM attacks occur
To conduct a man in the middle attack, the attacker needs to have a network position that allows them to observe and intercept messages in transit. After the attacker successfully positions themself in the communication path, three of the common malicious actions they take are to:
- Passively listen to the conversation, gaining access to confidential information (e.g., login credentials, credit card numbers, personal information, or sensitive business data)
- Alter the content of the communication (e.g., insert false information to mislead the recipient or to provoke certain responses) before passing the message along to the intended recipient. For example, in a banking transaction, an attacker could alter the account number, diverting funds to their account.
- Take over a session between a user and a server after authentication has been completed. This is a sophisticated type of attack during which the attacker can act as though they are the authenticated user to establish unauthorized connections or deliver malicious payloads.
Understanding the common techniques used for man in the middle attacks helps ensure that the right security defenses are in place to protect users and secure networks against these attacks.
The following are several techniques often used for man in the middle attacks.
Address Resolution Protocol (ARP) spoofing
Attackers manipulate ARP messages within a local network to associate their media access control (MAC) address with the internet protocol (IP) address of a legitimate device, often a gateway or router. Traffic intended for the legitimate device is then redirected to the attacker’s device. This allows attackers to intercept, modify, or block network traffic to conduct man-in-the-middle attacks.
Bluetooth attacks
Attackers exploit vulnerabilities in Bluetooth-enabled devices to compromise their security and intercept communication between paired devices.
Browser-based attacks
Vulnerabilities in web browsers and associated plugins are exploited to inject malicious code into legitimate websites. When users visit these sites, the malicious code executes.
Domain name system (DNS) spoofing
Also referred to as DNS cache poisoning, with a DNS spoofing attack, attackers compromise DNS servers or poison DNS caches, then redirect legitimate domain requests to malicious IP addresses they control.
Email spoofing
Attackers forge a legitimate email address in an email message by manipulating the email header information to make it appear as though the email came from a trusted source.
Extension spoofing
With extension spoofing, an attacker disguises a malicious file by changing its extension to appear as a harmless file type. For example, a malware .exe file might be renamed to look like a legitimate .pdf or .jpg file. When the recipient opens the file, the hidden malicious software is executed.
IP spoofing
An attacker creates IP packets with a forged source IP address to hide their identity or impersonate another system. By forging the source IP address, attackers can deceive network devices into accepting malicious traffic as legitimate.
Malicious proxy servers
Attackers set up proxy servers to intercept and relay communication between clients and servers, allowing them to eavesdrop on or manipulate the data passing through the proxy. These servers appear legitimate and are often able to evade detection.
Packet sniffing
Attackers use packet sniffing tools to capture and analyze network traffic.
Physical access
When attackers have physical access to network infrastructure or devices, they can directly intercept communication by tapping into network cables or installing rogue monitoring devices.
SSL stripping
Attackers downgrade secure Hypertext Transfer Protocol Secure (HTTPS) connections to unencrypted Hypertext Transfer Protocol (HTTP) by intercepting the initial HTTPS request and presenting a fake Secure Sockets Layer (SSL) certificate to the user’s browser.
Session hijacking
Attackers steal session cookies or tokens to impersonate authenticated users, gaining unauthorized access to their accounts and sensitive information.
Website or domain spoofing
Website spoofing is a type of man in the middle attack where the attacker uses a domain name that is very close to a legitimate website’s domain to trick users into thinking that they are interacting with a legitimate site. For example, a legitimate site would be organization.com, but the spoofed one would be organzation.com (dropping a letter) or organization.support.com (including a fake subdomain).
Wi-Fi eavesdropping
Attackers set up rogue Wi-Fi access points with names similar to legitimate networks to trick users into connecting to them. Once connected, the attacker can intercept and monitor all traffic passing through the compromised access point.
Preventing man in the middle attacks
Preventing a man-in-the-middle attack requires a combination of proactive security measures. Security tactics to help mitigate the risk of a man-in-the-middle attack are as follows.
Check network device configurations
Confirm that all routers, switches, and other network devices are optimally configured for security. This includes disabling unnecessary services and ensuring that default passwords are changed, as well as implementing secure protocols for remote management.
Continuously monitor networks
Network monitoring and intrusion detection systems can also be used to identify unusual activity that might indicate a man-in-the-middle attack. These tools provide real-time alerting and automated response mechanisms to mitigate threats as they are identified.
Educate users
Train users on the risks of man-in-the-middle attacks. Key areas to focus on are the importance of verifying the authenticity of websites before clicking links, checking attachments before opening them, confirming senders when reviewing emails, raising awareness of phishing and other social engineering tactics, and avoiding connecting to unsecured public Wi-Fi networks.
Employ certificate pinning
Implement certificate pinning to bind specific secure sockets layer and transport layer security (SSL/TLS) certificates to applications, preventing attackers from intercepting communication by presenting fraudulent certificates.
Encrypt communication channels
Implement strong encryption (e.g., SSL/TLS and virtual private networks (VPNs)) to protect communications and data in transit.
Install software updates and patches
Keep all software, operating systems, and firmware updated to eliminate vulnerabilities that attackers could exploit.
Segment networks
Isolate critical systems and sensitive data by dividing a network into multiple segments to restrict lateral movement, limiting attackers’ access and reducing their ability to compromise the entire network.
Use HTTPS
Always use HTTPS for websites to ensure that data is encrypted between the user’s browser and the website.
Don’t underestimate a man in the middle attack
Man in the middle attacks are common and often successful because of the many ways they can be executed. There are a number of options available to stop them. Often, they can be stopped using technology that is already in place and just applying it to prevent this type of attack.
The investment and effort to implement man-in-the-middle attack security is worth it. The systems that will safeguard against a man-in-the-middle attack will also provide additional security benefits.
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