--- name: analyzing-cobalt-strike-beacon-configuration-a387c7b1fe8a 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: Krishna Kumar (xalgord) license: Apache-2.0 nist_csf: - DE.AE-02 - RS.AN-03 - ID.RA-01 - DE.CM-01 --- # 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 ## Detection Gaps & Validation - **Sleep-mask encrypts the config in memory.** Modern beacons (CS 4.7+) and custom UDRLs mask the beacon and its config while sleeping, so a naive memory scan finds nothing between check-ins. Capture the dump while the beacon is awake, or defeat the mask, before concluding "no config." - **Non-default XOR keys and obfuscation.** The classic `0x2e`/`0x69` single-byte key and the default 4096-byte blob are often changed; obfuscated `.stage` transforms and stomped loaders break signature-only extraction. Run both `1768.py` (Didier Stevens) and SentinelOne `CobaltStrikeParser`/`dissect.cobaltstrike` and cross-check — one tool succeeding where another fails is common. - **Staged vs stageless.** A stager has no embedded config; you must pull the actual beacon from the team server or memory to recover C2 settings. - **Confirm a hit:** decode the TLV fields with a second tool, sanity-check that `SETTING_SLEEPTIME`/`SETTING_JITTER` match observed beacon intervals in the PCAP, and resolve the watermark against threat-intel watermark databases. - **False positives / benign lookalikes:** authorized red-team and pentest engagements use identical tooling; watermark `0` or widely-shared cracked watermarks indicate leaked kits, not attribution. Confirm the C2 is hostile (passive DNS, reputation) before escalating. ## 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 ### Step 1: Extract Configuration with CobaltStrikeParser ```python #!/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]} ") 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 ```python 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 ```python 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 ```python 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 - [SentinelOne CobaltStrikeParser](https://github.com/Sentinel-One/CobaltStrikeParser) - [dissect.cobaltstrike Library](https://github.com/fox-it/dissect.cobaltstrike) - [SentinelLabs Beacon Configuration Analysis](https://www.sentinelone.com/labs/the-anatomy-of-an-apt-attack-and-cobaltstrike-beacons-encoded-configuration/) - [Cobalt Strike Staging and Config Extraction](https://blog.securehat.co.uk/cobaltstrike/extracting-config-from-cobaltstrike-stager-shellcode) - [MITRE ATT&CK - Cobalt Strike S0154](https://attack.mitre.org/software/S0154/) --- Source attribution: xalgord Original project: https://github.com/xalgord/xalgorix/blob/cec44d71b1d998208e1e2091982d0ee2f928041f/internal/tools/skills/data/malware-analysis/analyzing-cobalt-strike-beacon-configuration/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: xalgord Original project: https://github.com/xalgord/xalgorix/blob/cec44d71b1d998208e1e2091982d0ee2f928041f/internal/tools/skills/data/malware-analysis/analyzing-cobalt-strike-beacon-configuration/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering Roles: Security Engineer Specialties: Specialty not specified Tools: Pefile, Volatility3, Windbg, Wireshark, Yara Python, Dissect.Cobaltstrike Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: c29422b553227e72ea2498b1a95daea3db786fd1cb961cf7ac9cc6c29d4a4f42