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hunting-for-cobalt-strike-beacons

Detect Cobalt Strike beacon command-and-control traffic using default TLS certificate signatures (serial 8BB00EE), JA3/JA3S/JARM fingerprints, HTTP malleable C2 profile pattern matching, and beacon jitter/interval analysis, built with Zeek network logs, Suricata IDS rules, and Python PCAP analysis. Use when hunting for Cobalt Strike beacon callbacks in network traffic or building detection rules for this C2 framework.

Published by mukul975 ↗mukul975/Anthropic-Cybersecurity-Skills

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Use hunting-for-cobalt-strike-beacons to analyze [PCAP or Zeek logs] for Cobalt Strike beacon indicators, including timing and HTTP-profile patterns, and return prioritized findings with detection-rule recommendations.

Required inputs

[PCAP or Zeek logs]

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SKILL.md

name: hunting-for-cobalt-strike-beaconsdescription: Detect Cobalt Strike beacon command-and-control traffic using default TLS certificate signatures (serial 8BB00EE), JA3/JA3S/JARM fingerprints, HTTP malleable C2 profile pattern matching, and beacon jitter/interval analysis, built with Zeek network logs, Suricata IDS rules, and Python PCAP analysis. Use when hunting for Cobalt Strike beacon callbacks in network traffic or building detection rules for this C2 framework.domain: cybersecuritysubdomain: threat-huntingtags: - cobalt-strike- beacon- threat-hunting- c2- zeek- suricata- ja3- jarm- network-forensicsversion: '1.0'author: mahipallicense: Apache-2.0nist_csf: - DE.CM-01- DE.AE-02- DE.AE-07- ID.RA-05mitre_attack: - T1046- T1057- T1082- T1083- T1071

Hunting for Cobalt Strike Beacons

Overview

Cobalt Strike is the most prevalent command-and-control framework used by both red teams and threat actors. Beacon, its primary payload, communicates with team servers using configurable HTTP/HTTPS/DNS profiles that can mimic legitimate traffic. However, default configurations and behavioral patterns remain detectable through TLS certificate analysis (default serial 8BB00EE), JA3/JA3S fingerprinting, beacon interval jitter analysis, and HTTP malleable profile pattern matching. This skill covers building detection capabilities using Zeek network logs, Suricata IDS rules, and Python-based PCAP analysis to identify beacon callbacks in network traffic.

When to Use

When investigating security incidents that require hunting for cobalt strike beacons
When building detection rules or threat hunting queries for this domain
When SOC analysts need structured procedures for this analysis type
When validating security monitoring coverage for related attack techniques

Prerequisites

Zeek 6.0+ with JA3 and HASSH packages installed
Suricata 7.0+ with Emerging Threats ruleset
Python 3.9+ with scapy and dpkt libraries
Network traffic captures (PCAP) or live Zeek logs
RITA (Real Intelligence Threat Analytics) for beacon scoring
Threat intelligence feeds with known Cobalt Strike IOCs

Steps

Step 1: TLS Certificate Analysis

Detect default Cobalt Strike certificates using JA3S fingerprints, certificate serial numbers, and JARM fingerprints in Zeek ssl.log.

Step 2: Beacon Interval Analysis

Analyze connection timing patterns to identify regular callback intervals with configurable jitter, characteristic of beacon behavior.

Step 3: HTTP Profile Detection

Match HTTP request patterns (URI paths, headers, user-agents) against known malleable C2 profiles.

Step 4: Correlate and Score

Combine multiple indicators (TLS + timing + HTTP profile) into a composite beacon confidence score.

Expected Output

JSON report containing detected beacon candidates with confidence scores, TLS fingerprints, timing analysis, HTTP profile matches, and recommended response actions.