Course 6 - Network Traffic Analysis for Incident Response | Episode 4: Mapping, Decoding, and Decrypting Network Traffic Intelligence

In this lesson, you’ll learn about: Intelligence Collection from Network Traffic Captures — focusing on anomalies, attacker behavior, and extracting actionable intelligence. 1. Network Mapping & VisualizationHumans struggle with long lists → visualizing traffic helps you feel the environment.Tools like pcap viz generate maps at different OSI layers:Layer 3 (IP Addresses)Shows which machines talk to each other.Helps detect unusual communication paths.Layer 4 (TCP/UDP Ports)Shows communication between applications.Unusual ports (e.g., 900) may indicate custom or C2 protocols.2. Content Deobfuscation Attackers often hide traffic with simple encodings (not strong encryption).Goal → recover the original content, often a payload or second-stage executable. XOR EncodingCommon in malware traffic.Repeated patterns in streams (especially when encoding zeros) reveal the key.Example: fixed-length 4-byte key like MLVR.Base64 (B64)Seen in C2 frameworks like Onion Duke.Recognizable by:A–Z, a–z, 0–9, “+”, “/”Ends with “=” paddingEasy to decode using built-in libraries or online tools.3. Credential Capture from Insecure Protocols Focus: credentials leaking in plaintext protocols. Telnet & IMAPSend usernames/passwords in clear text.Easy to extract directly from the TCP stream.SMTPEncodes credentials in Base64 → trivial to decode.Python or online decoders reveal username + password.Reinforces the need for TLS encryption.4. SSL/TLS Decryption in Wireshark Encrypted traffic looks like random “gibberish” unless you have the right keys. Using RSA Private KeysIf the RSA private key is available, Wireshark can decrypt sessions directly.Ephemeral Keys (ECDHE)Cannot be decrypted using the server’s private key.Must capture the session keys using a pre-master secret log file:Often done by setting an SSL key log file environment variable in browsers.Without that log, the sessions are not recoverable.5. Web Proxy Interception (Deep Packet Inspection) Enterprise method for inspecting encrypted HTTPS traffic. How it worksA corporate proxy (e.g., Burp Suite) intercepts connections:Breaks the client → server TLS session.Decrypts → inspects → re-encrypts all traffic.RequirementsClients must install the proxy’s self-signed root certificate.Needed to bypass controls like HSTS.RisksProxy becomes a single high-value target for attackers.Raises privacy concerns, especially when employees do personal browsing (banking, etc.).You can listen and download our episodes for free on more than 10 different platforms:https://linktr.ee/cybercode_academy