Man-in-the-Middle Attacks: How to Protect Your Communications

How Man-in-the-Middle Attacks Work

A man-in-the-middle (MITM) attack occurs when an attacker secretly intercepts and potentially alters communications between two parties who believe they are communicating directly with each other. The attacker positions themselves between the sender and receiver, reading, modifying, or injecting messages without either side being aware.

Imagine sending a sealed letter through a courier. In a MITM attack, someone intercepts the letter, opens it, reads the contents, possibly changes the message, reseals it, and delivers it to the recipient. Both you and the recipient believe the letter was delivered securely.

MITM attacks are particularly dangerous because they compromise the confidentiality and integrity of communications simultaneously. The attacker can steal sensitive data like login credentials, financial information, and personal messages while also injecting malicious content into otherwise legitimate communications.

Types of MITM Attacks

Wi-Fi Eavesdropping

The simplest MITM attack involves setting up a rogue Wi-Fi access point with a legitimate-sounding name like "Coffee_Shop_Free_WiFi" or "Airport_WiFi." When users connect, all their unencrypted traffic passes through the attacker's device. Even on legitimate public Wi-Fi networks, attackers on the same network can use tools to intercept traffic from other connected devices.

ARP Spoofing

Address Resolution Protocol (ARP) maps IP addresses to physical MAC addresses on a local network. An attacker can send forged ARP messages to associate their MAC address with another host's IP address, causing traffic intended for that host to be redirected through the attacker's machine. This is one of the most common MITM techniques on local area networks.

DNS Spoofing

DNS spoofing involves corrupting the DNS resolution process so that a domain name resolves to the attacker's IP address instead of the legitimate server. When you type "bank.com" into your browser, DNS spoofing could redirect you to a convincing replica hosted on the attacker's server. Any credentials you enter are captured.

SSL Stripping

SSL stripping downgrades an HTTPS connection to HTTP without the user's knowledge. When you navigate to a website, the attacker intercepts the server's HTTPS redirect and presents you with an unencrypted HTTP version of the site. The attacker maintains an encrypted connection to the real server while you communicate in plain text, unaware that your connection is not secure.

HTTPS Spoofing

More sophisticated attackers may present fraudulent SSL certificates to maintain the appearance of an encrypted connection. This requires the victim to ignore browser certificate warnings or the attacker to compromise a certificate authority — both of which have occurred in documented attacks.

Real-World Attack Scenarios

MITM attacks are not theoretical. In 2015, the Superfish adware pre-installed on Lenovo laptops installed a root certificate that allowed it to intercept all HTTPS traffic for ad injection — effectively creating a MITM vulnerability on every affected machine.

In 2017, researchers demonstrated that the KRACK vulnerability in WPA2 Wi-Fi encryption could be exploited to perform MITM attacks on wireless networks, affecting virtually every Wi-Fi device in existence at the time.

Nation-state actors have been documented performing MITM attacks at Internet exchange points, intercepting traffic at the infrastructure level to conduct surveillance on targeted populations.

Protection Against MITM Attacks

HTTPS and TLS

The most fundamental protection against MITM attacks is end-to-end encryption using TLS (Transport Layer Security). When you connect to a website over HTTPS, your browser and the server establish an encrypted channel that prevents eavesdropping. Always verify that the padlock icon is present in your browser's address bar before entering sensitive information.

HSTS (HTTP Strict Transport Security) headers prevent SSL stripping by instructing browsers to always use HTTPS for a given domain. Major browsers also maintain preloaded HSTS lists for high-value websites.

Certificate Pinning

Certificate pinning associates a specific server with its expected cryptographic certificate or public key. If an attacker attempts to use a different certificate (even one signed by a trusted CA), the connection is rejected. Mobile apps commonly implement certificate pinning to prevent MITM attacks on their API communications.

VPN Usage

A VPN encrypts all traffic between your device and the VPN server, preventing local network MITM attacks. This is especially important on public Wi-Fi networks where ARP spoofing and rogue access points are common threats.

End-to-End Encrypted Messaging

Messaging apps with end-to-end encryption (Signal, WhatsApp) ensure that messages can only be read by the sender and recipient. Even if an attacker intercepts the encrypted messages in transit, they cannot decrypt them. Use our Text Encryption tool to encrypt sensitive text before sending it through any communication channel.

DNS Security

Use DNS over HTTPS (DoH) or DNS over TLS (DoT) to encrypt your DNS queries, preventing DNS spoofing attacks. Configure your devices to use encrypted DNS providers like Cloudflare (1.1.1.1) or Google (8.8.8.8) with DoH enabled.

Verify Certificate Warnings

Never ignore browser certificate warnings. These warnings exist specifically to alert you to potential MITM attacks. If your browser warns that a site's certificate is invalid, untrusted, or has changed unexpectedly, do not proceed — especially for banking, email, or other sensitive services.

Encrypting Your Sensitive Communications

MITM attacks exploit the gap between the sender and receiver. Closing that gap with encryption is the definitive defense. For sensitive text that needs to travel through potentially insecure channels, our Text Encryption tool lets you encrypt messages client-side before transmission, ensuring that even if intercepted, the content remains unreadable. Combined with HTTPS, VPN usage on public networks, and attention to certificate warnings, you can effectively neutralize the threat of man-in-the-middle attacks.