hunting-for-cobalt-strike-beacons

by mukul975

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SKILL.md About

---
name: hunting-for-cobalt-strike-beacons
description: Detect Cobalt Strike beacon network activity using default TLS certificate signatures (serial 8BB00EE), JA3/JA3S/JARM
  fingerprints, HTTP C2 profile pattern matching, beacon jitter analysis, and named pipe detection via Zeek, Suricata, and
  Python PCAP analysis.
domain: cybersecurity
subdomain: threat-hunting
tags:
- cobalt-strike
- beacon
- threat-hunting
- c2
- zeek
- suricata
- ja3
- jarm
- network-forensics
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- DE.CM-01
- DE.AE-02
- DE.AE-07
- ID.RA-05
---

# 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.