Man-in-the-Middle Attacks

MITM attacks position attackers between communicating parties, enabling interception, modification, or blocking of traffic. Understanding these attacks reveals both offensive capabilities and defensive requirements.

Attack Positioning

MITM requires placing yourself in the communication path. On local networks, ARP spoofing associates your MAC address with the gateway IP, causing traffic to route through your system before reaching its destination.

DNS spoofing redirects traffic by providing false name resolution. If you control which IP addresses hostnames resolve to, you can redirect connections to systems you control.

Physical access to network infrastructure—switches, routers, or patch panels—provides interception without any active attack. This physical layer access is often overlooked in security assessments.

Rouge access points create wireless MITM positions. Clients connecting to attacker-controlled WiFi have all traffic available for inspection, even if encryption later protects some of that traffic.

Interception Capabilities

Once positioned, active interception examines passing traffic. Unencrypted protocols like HTTP reveal complete content—credentials, session tokens, sensitive data. Tools like Wireshark capture and analyze intercepted traffic.

Encrypted traffic resists content inspection. HTTPS protects data in transit. However, you can observe metadata: what servers are contacted, certificate properties, and traffic timing patterns. This metadata alone has intelligence value.

SSL/TLS interception becomes possible if clients accept invalid certificates. Corporate networks often deploy proxy certificates. Attack scenarios might use similar approaches if victims ignore certificate warnings.

Traffic Manipulation

Beyond passive interception, active attacks modify traffic in transit. Inject malicious content into unencrypted web responses. Modify software downloads to include malware. Alter transactions in real-time.

Protocol downgrade attacks force connections to less secure methods. Stripping HTTPS redirects might expose authentication. Forcing older TLS versions enables exploits against deprecated cipher suites.

Defensive Implications

Understanding MITM attacks informs defense priorities. HTTPS everywhere protects data in transit. HSTS prevents downgrade attacks. Certificate pinning detects illegitimate certificates.

Network monitoring might detect ARP anomalies or rogue access points. Proper network architecture limits local attacker capabilities. Defense in depth assumes some attacks succeed and focuses on limiting impact.