What it does. Extract and analyze Cobalt Strike beacon configuration from PE files Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).
Install
npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill analyzing-cobalt-strike-beacon-configuration, or copy the skill folder into ~/.claude/skills/analyzing-cobalt-strike-beacon-configuration/.- Raw file:
curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/analyzing-cobalt-strike-beacon-configuration/SKILL.md
SKILL.md (verbatim)
name: analyzing-cobalt-strike-beacon-configuration
description: Extract and analyze Cobalt Strike beacon configuration from PE files
and memory dumps to identify C2 infrastructure, malleable profiles, and operator
tradecraft.
domain: cybersecurity
subdomain: malware-analysis
tags:
- cobalt-strike
- beacon
- c2
- malware-analysis
- config-extraction
- threat-hunting
- red-team-tools
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- DE.AE-02
- RS.AN-03
- ID.RA-01
- DE.CM-01
mitre_attack:
- T1071.001
- T1573.001
- T1090.004
- T1105
- T1027
Analyzing Cobalt Strike Beacon Configuration
Overview
Cobalt Strike is a commercial adversary simulation tool widely abused by threat actors for post-exploitation operations. Beacon payloads contain embedded configuration data that reveals C2 server addresses, communication protocols, sleep intervals, jitter values, malleable C2 profile settings, watermark identifiers, and encryption keys. Extracting this configuration from PE files, shellcode, or memory dumps is critical for incident responders to map attacker infrastructure and attribute campaigns. The beacon configuration is XOR-encoded using a single byte (0x69 for version 3, 0x2e for version 4) and stored in a Type-Length-Value (TLV) format within the .data section.
When to Use
- When investigating security incidents that require analyzing cobalt strike beacon configuration
- 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
- Python 3.9+ with
dissect.cobaltstrike, pefile, yara-python
- SentinelOne CobaltStrikeParser (
parse_beacon_config.py)
- Hex editor (010 Editor, HxD) for manual inspection
- Understanding of PE file format and XOR encoding
- Memory dump acquisition tools (Volatility3, WinDbg)
- Network analysis tools (Wireshark) for C2 traffic correlation
Key Concepts
Beacon Configuration Structure
Cobalt Strike beacons store their configuration as a blob of TLV (Type-Length-Value) entries within the .data section of the PE. Stageless beacons XOR the entire beacon code with a 4-byte key. The configuration blob itself uses a single-byte XOR key. Each TLV entry contains a 2-byte type identifier (e.g., 0x0001 for BeaconType, 0x0008 for C2Server), a 2-byte length, and variable-length data.
Malleable C2 Profiles
The beacon configuration encodes the malleable C2 profile that dictates HTTP request/response transformations, including URI paths, headers, metadata encoding (Base64, NetBIOS), and data transforms. Analyzing these settings reveals how the beacon disguises its traffic to blend with legitimate web traffic.
Watermark and License Identification
Each Cobalt Strike license embeds a unique watermark (4-byte integer) into generated beacons. Extracting the watermark can link multiple beacons to the same operator or cracked license. Known watermark databases maintained by threat intelligence providers map watermarks to specific threat actors or leaked license keys.
Workflow
#!/usr/bin/env python3
"""Extract Cobalt Strike beacon config from PE or memory dump."""
import sys
import json
# Using SentinelOne's CobaltStrikeParser
# pip install dissect.cobaltstrike
from dissect.cobaltstrike.beacon import BeaconConfig
def extract_beacon_config(filepath):
"""Parse beacon configuration from file."""
configs = list(BeaconConfig.from_path(filepath))
if not configs:
print(f"[-] No beacon configuration found in {filepath}")
return None
for i, config in enumerate(configs):
print(f"\n[+] Beacon Configuration #{i+1}")
print(f"{'='*60}")
settings = config.as_dict()
# Critical fields for incident response
critical_fields = [
"SETTING_C2_REQUEST",
"SETTING_C2_RECOVER",
"SETTING_PUBKEY",
"SETTING_DOMAINS",
"SETTING_BEACONTYPE",
"SETTING_PORT",
"SETTING_SLEEPTIME",
"SETTING_JITTER",
"SETTING_MAXGET",
"SETTING_SPAWNTO_X86",
"SETTING_SPAWNTO_X64",
"SETTING_PIPENAME",
"SETTING_WATERMARK",
"SETTING_C2_VERB_GET",
"SETTING_C2_VERB_POST",
"SETTING_USERAGENT",
"SETTING_PROTOCOL",
]
for field in critical_fields:
value = settings.get(field, "N/A")
print(f" {field}: {value}")
return settings
return None
def extract_c2_indicators(config):
"""Extract actionable C2 indicators from beacon config."""
indicators = {
"c2_domains": [],
"c2_ips": [],
"c2_urls": [],
"user_agent": "",
"named_pipes": [],
"spawn_processes": [],
"watermark": "",
}
if not config:
return indicators
# Extract C2 domains
domains = config.get("SETTING_DOMAINS", "")
if domains:
for domain in str(domains).split(","):
domain = domain.strip().rstrip("/")
if domain:
indicators["c2_domains"].append(domain)
# Extract user agent
indicators["user_agent"] = str(config.get("SETTING_USERAGENT", ""))
# Extract named pipes
pipe = config.get("SETTING_PIPENAME", "")
if pipe:
indicators["named_pipes"].append(str(pipe))
# Extract spawn-to processes
for arch in ["SETTING_SPAWNTO_X86", "SETTING_SPAWNTO_X64"]:
proc = config.get(arch, "")
if proc:
indicators["spawn_processes"].append(str(proc))
# Extract watermark
indicators["watermark"] = str(config.get("SETTING_WATERMARK", ""))
return indicators
if __name__ == "__main__":
if len(sys.argv) < 2:
print(f"Usage: {sys.argv[0]} <beacon_file_or_dump>")
sys.exit(1)
config = extract_beacon_config(sys.argv[1])
if config:
indicators = extract_c2_indicators(config)
print(f"\n[+] Extracted C2 Indicators:")
print(json.dumps(indicators, indent=2))
Step 2: Manual XOR Decryption of Beacon Config
import struct
def find_and_decrypt_config(data):
"""Manually locate and decrypt beacon configuration."""
# Cobalt Strike 4.x uses 0x2e as XOR key
xor_keys = [0x2e, 0x69] # v4, v3
for xor_key in xor_keys:
# Search for the config magic bytes after XOR
# Config starts with 0x0001 (BeaconType) XOR'd with key
magic = bytes([0x00 ^ xor_key, 0x01 ^ xor_key,
0x00 ^ xor_key, 0x02 ^ xor_key])
offset = data.find(magic)
if offset == -1:
continue
print(f"[+] Found config at offset 0x{offset:x} (XOR key: 0x{xor_key:02x})")
# Decrypt the config blob (typically 4096 bytes)
config_size = 4096
encrypted = data[offset:offset + config_size]
decrypted = bytes([b ^ xor_key for b in encrypted])
# Parse TLV entries
entries = parse_tlv(decrypted)
return entries
return None
def parse_tlv(data):
"""Parse Type-Length-Value configuration entries."""
entries = {}
offset = 0
# TLV field type mapping
field_names = {
0x0001: "BeaconType",
0x0002: "Port",
0x0003: "SleepTime",
0x0004: "MaxGetSize",
0x0005: "Jitter",
0x0006: "MaxDNS",
0x0007: "Deprecated_PublicKey",
0x0008: "C2Server",
0x0009: "UserAgent",
0x000a: "PostURI",
0x000b: "Malleable_C2_Instructions",
0x000c: "Deprecated_HttpGet_Metadata",
0x000d: "SpawnTo_x86",
0x000e: "SpawnTo_x64",
0x000f: "CryptoScheme",
0x001a: "Watermark",
0x001d: "C2_HostHeader",
0x0024: "PipeName",
0x0025: "Year",
0x0026: "Month",
0x0027: "Day",
0x0036: "ProxyHostname",
}
while offset + 6 <= len(data):
entry_type = struct.unpack(">H", data[offset:offset+2])[0]
entry_len_type = struct.unpack(">H", data[offset+2:offset+4])[0]
entry_len = struct.unpack(">H", data[offset+4:offset+6])[0]
if entry_type == 0:
break
value_start = offset + 6
value_end = value_start + entry_len
value_data = data[value_start:value_end]
field_name = field_names.get(entry_type, f"Unknown_0x{entry_type:04x}")
if entry_len_type == 1: # Short
value = struct.unpack(">H", value_data[:2])[0]
elif entry_len_type == 2: # Int
value = struct.unpack(">I", value_data[:4])[0]
elif entry_len_type == 3: # String/Blob
value = value_data.rstrip(b'\x00').decode('utf-8', errors='replace')
else:
value = value_data.hex()
entries[field_name] = value
print(f" {field_name}: {value}")
offset = value_end
return entries
Step 3: YARA Rule for Beacon Detection
import yara
cobalt_strike_rule = """
rule CobaltStrike_Beacon_Config {
meta:
description = "Detects Cobalt Strike beacon configuration"
author = "Malware Analysis Team"
date = "2025-01-01"
strings:
// XOR'd config marker for CS 4.x (key 0x2e)
$config_v4 = { 2e 2f 2e 2c }
// XOR'd config marker for CS 3.x (key 0x69)
$config_v3 = { 69 68 69 6b }
// Common beacon strings
$str_pipe = "\\\\.\\pipe\\" ascii wide
$str_beacon = "beacon" ascii nocase
$str_sleeptime = "sleeptime" ascii nocase
// Reflective loader pattern
$reflective = { 4D 5A 41 52 55 48 89 E5 }
condition:
($config_v4 or $config_v3) or
(2 of ($str_*) and $reflective)
}
"""
def scan_for_beacons(filepath):
"""Scan file with YARA rules for Cobalt Strike beacons."""
rules = yara.compile(source=cobalt_strike_rule)
matches = rules.match(filepath)
for match in matches:
print(f"[+] YARA Match: {match.rule}")
for string_match in match.strings:
offset = string_match.instances[0].offset
print(f" String: {string_match.identifier} at offset 0x{offset:x}")
return matches
Step 4: Network Traffic Correlation
from dissect.cobaltstrike.c2 import HttpC2Config
def analyze_c2_profile(beacon_config):
"""Analyze malleable C2 profile from beacon configuration."""
print("\n[+] Malleable C2 Profile Analysis")
print("=" * 60)
# HTTP GET configuration
get_verb = beacon_config.get("SETTING_C2_VERB_GET", "GET")
get_uri = beacon_config.get("SETTING_C2_REQUEST", "")
print(f"\n HTTP GET Request:")
print(f" Verb: {get_verb}")
print(f" URI: {get_uri}")
# HTTP POST configuration
post_verb = beacon_config.get("SETTING_C2_VERB_POST", "POST")
post_uri = beacon_config.get("SETTING_C2_POSTREQ", "")
print(f"\n HTTP POST Request:")
print(f" Verb: {post_verb}")
print(f" URI: {post_uri}")
# User Agent
ua = beacon_config.get("SETTING_USERAGENT", "")
print(f"\n User-Agent: {ua}")
# Host header
host = beacon_config.get("SETTING_C2_HOSTHEADER", "")
print(f" Host Header: {host}")
# Sleep and jitter for traffic pattern
sleep_ms = beacon_config.get("SETTING_SLEEPTIME", 60000)
jitter = beacon_config.get("SETTING_JITTER", 0)
print(f"\n Sleep Time: {sleep_ms}ms")
print(f" Jitter: {jitter}%")
# Generate Suricata/Snort signatures
print(f"\n[+] Suggested Network Signatures:")
if ua:
print(f' alert http any any -> any any (msg:"CS Beacon UA"; '
f'content:"{ua}"; http_user_agent; sid:1000001; rev:1;)')
if get_uri:
print(f' alert http any any -> any any (msg:"CS Beacon URI"; '
f'content:"{get_uri}"; http_uri; sid:1000002; rev:1;)')
Validation Criteria
- Beacon configuration successfully extracted from PE file or memory dump
- C2 server domains/IPs correctly identified with port and protocol
- Malleable C2 profile parameters decoded showing HTTP transforms
- Watermark value extracted for attribution correlation
- Sleep time and jitter values match observed network beacon intervals
- YARA rules detect beacon in both packed and unpacked samples
- Network signatures generated from extracted C2 profile
References
Other files in this skill
assets/template.md (verbatim)
Cobalt Strike Beacon Analysis Report Template
| Field |
Value |
| Report ID |
CS-BEACON-YYYY-NNNN |
| Date |
YYYY-MM-DD |
| Sample Hash (SHA-256) |
|
| Classification |
TLP:AMBER |
| Analyst |
|
Beacon Configuration Summary
| Setting |
Value |
| Beacon Type |
HTTP / HTTPS / SMB / DNS |
| C2 Server(s) |
|
| Port |
|
| Sleep Time |
ms |
| Jitter |
% |
| User-Agent |
|
| Watermark |
|
| SpawnTo (x86) |
|
| SpawnTo (x64) |
|
| Named Pipe |
|
| Host Header |
|
| Crypto Scheme |
|
C2 Infrastructure
| Indicator |
Type |
Value |
Context |
| C2 Domain |
domain |
|
Primary callback |
| C2 IP |
ip |
|
Resolved address |
| URI Path (GET) |
uri |
|
Beacon check-in |
| URI Path (POST) |
uri |
|
Data exfiltration |
Malleable C2 Profile
HTTP GET Configuration
| Parameter |
Value |
| URI |
|
| Verb |
|
| Headers |
|
| Metadata Encoding |
|
HTTP POST Configuration
| Parameter |
Value |
| URI |
|
| Verb |
|
| ID Encoding |
|
| Output Encoding |
|
Watermark Attribution
| Watermark |
Known Association |
Confidence |
|
Cracked / Licensed / Threat Actor |
High/Med/Low |
Network Detection Signatures
# Suricata signature for beacon C2 traffic
alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"Cobalt Strike Beacon C2 Communication";
content:"[USER_AGENT]"; http_user_agent;
content:"[URI_PATH]"; http_uri;
sid:1000001; rev:1;
)
YARA Detection Rule
rule CobaltStrike_Beacon_[CAMPAIGN] {
meta:
description = "Detects Cobalt Strike beacon from [CAMPAIGN]"
hash = "[SHA256]"
strings:
$c2 = "[C2_DOMAIN]" ascii
$pipe = "[NAMED_PIPE]" ascii
$ua = "[USER_AGENT]" ascii
condition:
2 of them
}
Recommendations
- Block: Add C2 domains/IPs to firewall deny lists
- Hunt: Search for named pipe and spawn-to process in endpoint logs
- Detect: Deploy YARA and network signatures to detection stack
- Correlate: Check watermark against threat intelligence databases
references/api-reference.md (verbatim)
API Reference: Cobalt Strike Beacon Configuration Analysis
Structure
[Field ID: 2 bytes][Type: 2 bytes][Value: variable]
Type 1 = short (2 bytes), Type 2 = int (4 bytes), Type 3 = string/blob (2-byte length + data)
XOR Encoding
| Version |
XOR Key |
| CS 3.x |
0x69 |
| CS 4.x |
0x2E |
Key Configuration Fields
| ID |
Name |
Description |
| 1 |
BeaconType |
0=HTTP, 1=Hybrid, 2=SMB, 8=HTTPS |
| 2 |
Port |
C2 communication port |
| 3 |
SleepTime |
Beacon interval (ms) |
| 5 |
Jitter |
Random sleep variation (%) |
| 7 |
PublicKey |
RSA public key for encryption |
| 8 |
C2Server |
Command and control server(s) |
| 9 |
UserAgent |
HTTP User-Agent string |
| 10 |
PostURI |
POST callback URI |
| 37 |
Watermark |
License watermark (operator ID) |
| 54 |
PipeName |
Named pipe for SMB beacons |
Syntax
python 1768.py <beacon_file> # Extract config
python 1768.py -j <beacon_file> # JSON output
python 1768.py -r <beacon_file> # Raw config dump
CobaltStrikeParser (SentinelOne)
Syntax
python parse_beacon_config.py <file>
python parse_beacon_config.py --json <file>
Output Fields
BeaconType: HTTPS
Port: 443
SleepTime: 60000
Jitter: 37
C2Server: update.microsoft-cdn.com,/api/v2
UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
Watermark: 305419896
SpawnToX86: %windir%\syswow64\dllhost.exe
SpawnToX64: %windir%\sysnative\dllhost.exe
JARM Fingerprinting
Cobalt Strike Default JARM
# Default CS JARM hash (pre-4.7)
07d14d16d21d21d07c42d41d00041d24a458a375eef0c576d23a7bab9a9fb1
# Scan with JARM
python jarm.py <target_ip> -p 443
Known Watermark Values
| Watermark |
Attribution |
| 0 |
Trial/cracked version |
| 305419896 |
Common cracked version |
| 1359593325 |
Known threat actor toolkit |
| 1580103824 |
Known APT usage |
Detection Signatures
Suricata
alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"ET MALWARE Cobalt Strike Beacon";
content:"/submit.php"; http_uri;
content:"Cookie:"; http_header;
pcre:"/Cookie:\s[A-Za-z0-9+/=]{60,}/H";
sid:2028591; rev:1;)
YARA
rule CobaltStrike_Beacon {
strings:
$config_v3 = { 00 01 00 01 00 02 ?? ?? 00 01 00 02 }
$magic = "MSSE-%d-server"
$pipe = "\\\\.\\pipe\\msagent_"
condition:
uint16(0) == 0x5A4D and any of them
}
Malleable C2 Profile Elements
| Element |
Description |
http-get |
GET request profile (URI, headers, metadata transform) |
http-post |
POST request profile (URI, body transform) |
set sleeptime |
Default beacon interval |
set jitter |
Randomization percentage |
set useragent |
HTTP User-Agent |
set pipename |
SMB named pipe name |
references/standards.md (verbatim)
Standards and Frameworks Reference
Cobalt Strike Beacon Configuration Fields
Configuration TLV Types
| Type ID |
Field Name |
Data Type |
Description |
| 0x0001 |
BeaconType |
Short |
0=HTTP, 1=Hybrid HTTP/DNS, 8=HTTPS, 10=TCP Bind |
| 0x0002 |
Port |
Short |
C2 communication port |
| 0x0003 |
SleepTime |
Int |
Beacon callback interval in milliseconds |
| 0x0005 |
Jitter |
Short |
Percentage of sleep time randomization (0-99) |
| 0x0008 |
C2Server |
String |
Comma-separated C2 domains/IPs |
| 0x0009 |
UserAgent |
String |
HTTP User-Agent header value |
| 0x000a |
PostURI |
String |
URI for HTTP POST requests |
| 0x000d |
SpawnTo_x86 |
String |
32-bit process to spawn for post-ex |
| 0x000e |
SpawnTo_x64 |
String |
64-bit process to spawn for post-ex |
| 0x001a |
Watermark |
Int |
License watermark identifier |
| 0x0024 |
PipeName |
String |
Named pipe for SMB beacon |
| 0x001d |
HostHeader |
String |
HTTP Host header value |
| 0x0032 |
ProxyHostname |
String |
Proxy server address |
XOR Encoding Scheme
- Cobalt Strike 3.x: XOR key = 0x69
- Cobalt Strike 4.x: XOR key = 0x2e
- Configuration blob size: 4096 bytes (typical)
- Encoding: Single-byte XOR across entire config blob
Stageless Beacon Structure
- PE with beacon code in .data section
- 4-byte XOR key applied to .data section content
- Configuration embedded after beacon code
- Reflective DLL loader prepended to beacon
MITRE ATT&CK Mappings
Cobalt Strike Techniques (S0154)
| Technique |
ID |
Description |
| Application Layer Protocol |
T1071.001 |
HTTP/HTTPS C2 communication |
| Encrypted Channel |
T1573.002 |
AES-256 encrypted C2 |
| Ingress Tool Transfer |
T1105 |
Download additional payloads |
| Process Injection |
T1055 |
Inject into spawned processes |
| Named Pipes |
T1570 |
SMB beacon lateral movement |
| Service Execution |
T1569.002 |
PSExec-style lateral movement |
| Reflective Code Loading |
T1620 |
In-memory beacon loading |
Malleable C2 Profile Structure
HTTP GET Block
http-get {
set uri "/path";
client {
header "Accept" "text/html";
metadata {
base64url;
prepend "session=";
header "Cookie";
}
}
server {
header "Content-Type" "text/html";
output {
print;
}
}
}
HTTP POST Block
http-post {
set uri "/submit";
client {
id {
uri-append;
}
output {
base64;
print;
}
}
server {
output {
print;
}
}
}
References
references/workflows.md (verbatim)
Cobalt Strike Beacon Analysis Workflows
[Suspicious PE] --> [Unpack if packed] --> [Locate .data section] --> [XOR Decrypt]
|
v
[Parse TLV Config]
|
v
[Extract C2 Indicators]
Steps:
- Triage: Identify file as potential Cobalt Strike beacon via YARA or AV detection
- Unpacking: If packed, unpack using appropriate tool (UPX, custom unpacker)
- Section Analysis: Locate .data section containing XOR'd beacon code
- XOR Key Discovery: Try known keys (0x2e, 0x69) or brute-force 4-byte key
- Config Parsing: Parse decrypted TLV entries for C2 and operational settings
- IOC Extraction: Extract domains, IPs, URIs, user agents, watermarks
[Memory Dump] --> [Volatility3 malfind] --> [Dump Injected Regions] --> [Parse Config]
|
v
[C2 Infrastructure Map]
Steps:
- Acquisition: Capture memory dump from compromised system
- Process Scan: Use Volatility3 to identify suspicious processes
- Injection Detection: Use malfind to find RWX memory regions
- Region Extraction: Dump injected memory regions to files
- Config Search: Scan dumps for beacon configuration signatures
- Infrastructure Mapping: Correlate extracted C2 with network logs
Workflow 3: Watermark Attribution
[Multiple Beacons] --> [Extract Watermarks] --> [Cluster by Watermark] --> [Attribution]
|
v
[Campaign Correlation]
Steps:
- Collection: Gather beacon samples from incident or threat intel feeds
- Watermark Extraction: Extract watermark value from each sample
- Database Lookup: Check watermark against known databases
- Clustering: Group beacons sharing the same watermark
- Infrastructure Overlap: Correlate C2 infrastructure across cluster
- Attribution Assessment: Link to known threat actor or cracked license
Workflow 4: C2 Traffic Detection
[Beacon Config] --> [Extract C2 Profile] --> [Generate Signatures] --> [Deploy to NIDS]
|
v
[Monitor Network Traffic]
Steps:
- Profile Extraction: Parse malleable C2 profile from beacon config
- Pattern Identification: Identify unique HTTP headers, URIs, and encoding
- Signature Creation: Write Suricata/Snort rules matching C2 patterns
- Deployment: Deploy signatures to network detection infrastructure
- Validation: Test signatures against captured beacon traffic
- Monitoring: Alert on matching network flows for active beacons
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