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A man-in-the-middle attack (MitM) is a type of cyberattack in which the attacker secretly takes over or intercepts communications between two parties without the parties involved realizing. The attacker gets between the two parties (hence “man in the middle”), intercepts their data transmissions, and uses this position to spy on or even manipulate this data.
How does a man-in-the-middle attack work?
A MitM attack involves several steps and techniques to successfully intercept communication participants and gather or manipulate the transmitted information.
Establishing the connection
The attacker strategically positions themselves between the two parties who wish to communicate. This can be done in various ways, e.g.:
- ARP spoofing: In local area networks (LANs), the attacker can use spoofed ARP (Address Resolution Protocol) messages to trick network devices into routing their traffic through the attacker instead of directly to the actual destination.
- DNS Cache Poisoning: The attacker manipulates DNS (Domain Name System) responses to redirect traffic and gain control of it.
- Wi-Fi eavesdropping: In public Wi-Fi networks, the attacker can set up a rogue access point that appears to be a legitimate network access point. Users connect to this access point, which routes all their traffic through the attacker.
Intercepting data
Once the attacker is in the communication chain, they can intercept the traffic passing through. The data exchanged between the original parties now flows through the attacker, who can view, record, and analyze it.
Data manipulation
In addition to simple interception, the attacker can also modify the transmitted data. For example, they could change the transfer details during a bank transaction so that the money is transferred to the attacker’s account instead of the intended account.
Forwarding
In many cases, the attacker forwards the intercepted or manipulated data to the original recipient to avoid detection. This gives them the opportunity to remain undetected for a longer period of time and continue to intercept or modify data.
What variants of man-in-the-middle attacks are there?
A Man-in-the-middle attack can be carried out in different ways, depending on which vulnerabilities are exploited or which methods the attacker uses.
ARP spoofing
ARP (Address Resolution Protocol) spoofing is a common method for a Man-in-the-middle attack in local area networks (LANs). The attacker sends spoofed ARP messages into the network to trick network devices into routing their traffic through the attacker by making them think that the attacker’s IP address matches the MAC address of another device on the network.
DNS cache poisoning
In DNS cache poisoning, the attacker manipulates DNS responses to redirect traffic and gain control of it. This can result in users being unknowingly redirected to fake or malicious websites while believing they are accessing legitimate websites.
SSL stripping
SSL stripping is a technique where the attacker downgrades the security measures of an encrypted HTTPS connection to an unencrypted HTTP connection. This allows the attacker to see and manipulate the transmitted data, as it is no longer encrypted.
Wi-Fi eavesdropping
Wi-Fi eavesdropping often occurs on public networks where the attacker creates a malicious access point that looks similar to legitimate networks. Users who connect to this access point send all their traffic through the attacker, who can then intercept the data.
Session hijacking
In session hijacking, the attacker steals the session cookies that contain authentication information while a session is active. This allows the attacker to take control of a running session without knowing a visitor’s username and password.
Honeypot and fake access points
Attackers can also set up so-called honeypots or fake access points that resemble legitimate network services. Users connecting to such access points think they are using secure services, when in reality their data is being filtered and intercepted by the attacker.
Man-in-the-browser
Man-in-the-browser attacks take place at the web browser level by installing malicious code, such as a Trojan, in the user’s browser. This code can then manipulate transactions or spy on confidential information.
These different types of MitM attacks utilize different techniques and vulnerabilities, making them a versatile and dangerous threat in cybersecurity. Knowledge of these methods is crucial in order to take appropriate protective measures.
What security measures can be taken?
To MitM attacks, it is essential to implement both technical security measures and develop a general awareness of the risks and signs of such attacks.
Use of HTTPS
Care should be taken to always use a secure connection (HTTPS) when surfing the Internet. This can be recognized by the lock symbol in the address bar of the browser. HTTPS encrypts the data between the web browser and the server, which makes eavesdropping more difficult.
VPN use
A Virtual Private Network (VPN) should be used, especially when using public Wi-Fi networks. A VPN encrypts all data traffic from the device to the VPN server, which minimizes the risk of MitM attacks on insecure networks.
Strong authentication
Strong authentication mechanisms such as two-factor authentication (2FA) or multi-factor authentication (MFA) should be implemented. These additional security levels make it more difficult for attackers to impersonate legitimate users.
Check security certificates
You should regularly check whether the security certificates of websites are correct to ensure that you do not end up on fake pages created by DNS cache poisoning. Browser warnings about certificate problems should be taken seriously.
Updating software
Operating systems, applications, and network devices should always be kept up to date. Software updates often close security gaps that could be exploited by attackers.
Encrypted communication protocols
Encrypted communication protocols, such as SSH instead of Telnet or SFTP instead of FTP, should be used to protect data during transmission.
Secure Wi-Fi settings
Strong, hard-to-guess passwords for Wi-Fi networks should be used, and the use of public Wi-Fi networks for sensitive transactions should be avoided. For businesses, the use of a secure Wi-Fi authentication scheme such as WPA2-Enterprise is recommended.
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