Corporate laptops and production servers typically have robust security monitoring in place to reduce risk and meet compliance requirements. However, CI/CD runners, which handle sensitive information like secrets for cloud environments and create production builds, often lack such security measures. This oversight has led to significant supply chain attacks, including the SolarWinds and Codecov breaches.
Traditional security monitoring and EDR solutions are ineffective for CI/CD runners due to their ephemeral nature. These tools also lack the necessary context to correlate events with specific workflow runs in a CI/CD environment.
StepSecurity Harden-Runner addresses this gap by providing security monitoring tailored for CI/CD runners. This approach brings CI/CD runners under the same level of security scrutiny as other critical systems, addressing a significant gap in the software supply chain.
### Harden-Runner: Security Incidents Detected
- [Harden-Runner Detected the tj-actions/changed-files compromise](https://www.stepsecurity.io/blog/harden-runner-detection-tj-actions-changed-files-action-is-compromised) ([CVE-2025-30066](https://github.com/advisories/GHSA-mrrh-fwg8-r2c3))
- [Harden-Runner Detected a CI/CD Supply Chain Attack in Google’s Open-Source Project Flank](https://www.stepsecurity.io/case-studies/flank)
- [Harden-Runner Detected the NX Build System compromise](https://www.stepsecurity.io/blog/supply-chain-security-alert-popular-nx-build-system-package-compromised-with-data-stealing-malware)
- [Harden-Runner Detected a CI/CD Supply Chain Attack in Microsoft’s Open-Source Project Azure Karpenter Provider in Real-Time](https://www.stepsecurity.io/case-studies/azure-karpenter-provider)
- [Harden-Runner Detected Anomalous Traffic to api.ipify.org Across Multiple Customers](https://www.stepsecurity.io/blog/harden-runner-detects-anomalous-traffic-to-api-ipify-org-across-multiple-customers)
- [Harden-Runner Detected an Unexpected Microsoft Defender Installation on GitHub-Hosted Ubuntu Runners](https://www.stepsecurity.io/blog/how-stepsecurity-harden-runner-detected-unexpected-microsoft-defender-installation-on-github-hosted-ubuntu-runners)
- [Harden-Runner Flagged an Anomalous Outbound Call, Leading to a Docker Documentation Update](https://www.stepsecurity.io/blog/harden-runner-flags-anomalous-outbound-call-leading-to-docker-documentation-update)
### See It in Action
Harden-Runner secures over **8 million CI/CD workflow runs every week**, protecting thousands of pipelines, including those from popular open-source projects by **Microsoft, Google, and CISA**. See how top projects are using Harden-Runner and explore the insights:
➡️ [Who's using Harden-Runner?](https://docs.stepsecurity.io/whos-using-harden-runner)
Harden-Runner GitHub Action installs a security agent on the GitHub-hosted runner (Ubuntu VM) to
## Introduction
1. Prevent exfiltration of credentials
2. Detect tampering of source code during build
3. Detect compromised dependencies and build tools
Learn how Harden-Runner works through the video below, which shows how it detected the tj-actions/changed-files compromise. [View the interactive demo here](https://app.storylane.io/share/679y2zgzljov).
<img src="images/case-study.png" alt="Harden-Runner detected the tj-actions/changed-files Breach" title="This case study video shows how StepSecurity Harden-Runner detected the tj-actions/changed-files Breach">
</a>
<p align="left">
<img src="images/main-screenshot1.png" alt="Policy recommended by harden-runner">
</p>
---
## Getting Started
## Why
This guide walks you through the steps to set up and use Harden-Runner in your CI/CD workflows. For more details, refer to the [official documentation](https://docs.stepsecurity.io/harden-runner).
Compromised dependencies and build tools typically make outbound calls to exfiltrate credentials, or may tamper source code, dependencies, or artifacts during the build.
### **Step 1: Add Harden-Runner to Your Workflow**
Harden-Runner GitHub Actions installs a daemon that monitors process, file, and network activity to:
| 1. | Block outbound calls that are not in the allowed list to prevent exfiltration of credentials | To prevent [Codecov breach](https://github.com/step-security/attack-simulator/blob/main/docs/RestrictOutboundTraffic.md) scenario |
| 2. | Detect if source code is being overwritten during the build process to inject a backdoor | To detect [SolarWinds incident scenario](https://github.com/step-security/attack-simulator/blob/main/docs/MonitorSourceCode.md) |
| 3. | Detect compromised dependencies that make unexpected outbound network calls | To detect [Dependency confusion](https://github.com/step-security/attack-simulator/blob/main/docs/DNSExfiltration.md) and [Malicious dependencies](https://github.com/step-security/attack-simulator/blob/main/docs/CompromisedDependency.md) |
Read this [case study](https://infosecwriteups.com/detecting-malware-packages-in-github-actions-7b93a9985635) on how Harden-Runner detected malicious packages in the NPM registry.
## How
1. Add `step-security/harden-runner` to your GitHub Actions workflow file as the first step in each job.
To integrate Harden-Runner, follow these steps:
- Open your GitHub Actions workflow file (e.g., `.github/workflows/<workflow-name>.yml`).
- Add the following code as the first step in each job:
2. In the workflow logs, you will see a link to security insights and recommendations.
**Tip**: Automate this step by pasting your workflow into the [StepSecurity online tool](https://app.stepsecurity.io/secure-workflow)
<details>
<summary>Click to view the full Getting Started Guide</summary>
<p align="left">
<img src="images/buildlog1.png" alt="Link in build log" >
### **Step 2: Access Security Insights**
Run your workflow. Once completed:
- Review the **workflow logs** and the **job markdown summary**.
- Look for a link to **security insights and recommendations**.
<p align="left">
<img src="images/buildlog1.png" alt="Link in workflow log" >
</p>
- Click on the provided link (e.g., [example link](https://app.stepsecurity.io/github/step-security/github-actions-goat/actions/runs/7704454287?jobid=20996777560&tab=network-events)) to access the **Process Monitor View**, which displays:
- **Network events**: Outbound network calls correlated with each step.
- **File events**: File writes tracked during the job.
<p align="left">
<img src="images/network-events.png" alt="Link in network events" >
</p>
3. Click on the link ([example link](https://app.stepsecurity.io/github/ossf/scorecard/actions/runs/2265028928)). You will see a process monitor view of file and network activities correlated with each step of the job.
</details>
<p align="left">
<img src="images/insights2.png" alt="Insights from harden-runner" >
</p>
---
## Why Choose Harden-Runner?
4. Below the insights, you will see the recommended policy. Update your workflow file with the recommended policy.
- **Prevent Exfiltration:** Prevent the exfiltration of CI/CD secrets and source code.
- **Detect Tampering:** Identify source code modifications during builds.
- **Anomaly Detection:** Spot unusual dependencies and workflow behaviors.
- **Simplify Permissions:** Determine the minimum required `GITHUB_TOKEN` permissions.
<p align="left">
<img src="images/rec-policy1.png" alt="Policy recommended by harden-runner" >
</p>
## Features at a glance
---
For details, check out the documentation at https://docs.stepsecurity.io
## Features
### Restrict egress traffic to allowed endpoints
Harden-Runner offers a comprehensive suite of features to enhance the security of your CI/CD workflows, available in two tiers: **Community** (Free) and **Enterprise** (Paid).
Once allowed endpoints are set in the workflow file,
### Community (Free)
- Harden-Runner blocks egress traffic at the DNS (Layer 7) and network layers (Layers 3 and 4).
- It blocks DNS exfiltration, where attacker tries to send data out using DNS resolution
- Blocks outbound traffic using IP tables
- **CI/CD-Aware Event Correlation:** Each outbound network connection, file operation, and process execution is mapped to the exact step, job, and workflow where it occurs.
- **Automated Baseline Creation:** Harden-Runner builds a baseline for each job based on past outbound network connections.
- **Anomaly Detection:** Once the baseline is created, any future outbound calls not in the baseline trigger a detection.
- **Block Network Egress Traffic with Domain Allowlist:** Optionally use the automatically created baseline to control outbound network traffic by specifying allowed domains, preventing unauthorized data exfiltration.
- **Detect Modification of Source Code:** Monitor and alert on unauthorized changes to your source code during the CI/CD pipeline.
<p align="left">
<img src="images/block-outbound-call.png" alt="Policy recommended by harden-runner" >
</p>
### Enterprise (Paid)
### Detect tampering of source code during build
Includes all features in the **Community** tier, plus:
Harden-Runner monitors file writes and can detect if a file is overwritten.
- **Support for Private Repositories:** Extend Harden-Runner's security capabilities to your private GitHub repositories.
- **Support for Self-Hosted Runners:** Apply security controls and monitoring to self-hosted GitHub Actions runners.
- **GitHub Checks Integration:** Enable GitHub Checks for Harden-Runner—if the baseline remains unchanged, the check passes; if it changes, the check fails, showing new outbound connections.
- **View Outbound GitHub API calls at the Job Level:** Monitor HTTPS requests to GitHub APIs
- **Determine Minimum GITHUB_TOKEN Permissions:** Monitor outbound HTTPS requests to GitHub APIs to recommend the least-privilege permissions needed for your workflows, enhancing security by reducing unnecessary access.
- **View the Name and Path of Every File Written During the Build Process:** Gain visibility into every file written to the build environment, including the ability to correlate file writes with processes, ensuring complete transparency.
- **View Process Names and Arguments:** Monitor every process executed during the build process, along with its arguments, and navigate the process tree to detect suspicious activities.
- Source code overwrite is not expected in a release build
- All source code files are monitored, which means even changes to IaC files (Kubernetes manifest, Terraform) are detected
- You can enable notifications to get one-time alert when source code is overwritten
For a detailed comparison and more information, please visit our [Pricing Page](https://www.stepsecurity.io/pricing).
<p align="left">
<img src="images/fileoverwrite.png" alt="Policy recommended by harden-runner" >
</p>
Explore the full feature set in the [Features Documentation](https://docs.stepsecurity.io/harden-runner).
### Run your job without sudo access
---
GitHub-hosted runner uses passwordless sudo for running jobs.
## Trusted By and Case Studies
- This means compromised build tools or dependencies can install attack tools
- If your job does not need sudo access, you see a policy
recommendation to disable sudo in the insights page
- When you set `disable-sudo` to `true`, the job steps run without sudo access to the Ubuntu VM
Harden-Runner is trusted by over 8000 leading open-source projects andenterprises, including Microsoft, Google, Kubernetes, and more.
### Get security alerts
### Trusted by
Install the [Harden Runner App](https://github.com/marketplace/harden-runner-app) to get security alerts.
- Email and Slack notifications are supported
- Notifications are sent when outbound traffic is blocked or source code is overwritten
- Notifications are not repeated for the same alert for a given workflow
Private repositories are supported if they have a commercial license. Check out the [documentation](https://docs.stepsecurity.io/harden-runner/installation/business-enterprise-license) for more details.
- [How Coveo Strengthened GitHub Actions Security with StepSecurity](https://www.stepsecurity.io/case-studies/coveo)
- [Hashgraph Achieves Comprehensive CI/CD Security Without Compromising Development Speed](https://www.stepsecurity.io/case-studies/hashgraph)
- [Chainguard Secures GitHub Actions with StepSecurity](https://www.stepsecurity.io/case-studies/chainguard)
- [Kapiche secures their GitHub Actions software supply chain with Harden-Runner](https://www.stepsecurity.io/case-studies/kapiche)
- [Arcjet Enhances CI/CD Security with Harden-Runner](https://www.stepsecurity.io/case-studies/arcjet)
Install the [Harden Runner App](https://github.com/marketplace/harden-runner-app) to use Harden-Runner GitHub Action for `Private` repositories.
---
- If you use Harden-Runner GitHub Action in a private repository, the generated insights URL is NOT public.
- You need to authenticate first to access insights URL for private repository. Only those who have access to the repository can view it.
- [Harden Runner App](https://github.com/marketplace/harden-runner-app) only needs `actions: read` permissions on your repositories.
## Environment Compatibility Matrix
Read this [case study on how Kapiche uses Harden Runner](https://www.stepsecurity.io/case-studies/kapiche/) to improve software supply chain security in their open source and private repositories.
Harden-Runner is designed to work seamlessly across a variety of runner environments, providing consistent security insights and protections regardless of where your workflows execute. For self-hosted runners, audit mode is deployed directly to the runner infrastructure without requiring any changes to your existing workflows. For more details, refer to the [official documentation](https://docs.stepsecurity.io/harden-runner).
## Discussions
| Environment Type | Compatibility | Audit Mode Deployment | Workflow Changes for Audit Mode |
| GitHub-hosted runners | ✅ Full support | Add Harden-Runner Action to workflow | Yes |
| Self-hosted VM runners | ✅ Full support | Include agent in runner image | No |
| Self-hosted bare-metal runners | ✅ Full support | Install agent as a service | No |
| Actions Runner Controller (ARC) | ✅ Full support | Deploy as DaemonSet | No |
| RunsOn Runners | ✅ Full support | Pre-integrated | No |
If you have questions or ideas, please use [discussions](https://github.com/step-security/harden-runner/discussions).
## How It Works
1. [Support for private repositories](https://github.com/step-security/harden-runner/discussions/74)
2. [Where should allowed-endpoints be stored?](https://github.com/step-security/harden-runner/discussions/84)
3. [Cryptographically verify tools run as part of the CI/ CD pipeline](https://github.com/step-security/harden-runner/discussions/94)
Want to know the technical details? Dive into the architecture of Harden-Runner and its integrations for GitHub-hosted and self-hosted runners in our [How Harden-Runner Works Documentation](docs/how-it-works.md).
---
## Limitations
1. Harden-Runner GitHub Action only works for GitHub-hosted runners. Self-hosted runners are not supported.
2. Only Ubuntu VM is supported. Windows and MacOS GitHub-hosted runners are not supported. There is a discussion about that [here](https://github.com/step-security/harden-runner/discussions/121).
3. Harden-Runner is not supported when [job is run in a container](https://docs.github.com/en/actions/using-jobs/running-jobs-in-a-container) as it needs sudo access on the Ubuntu VM to run. It can be used to monitor jobs that use containers to run steps. The limitation is if the entire job is run in a container. That is not common for GitHub Actions workflows, as most of them run directly on `ubuntu-latest`.
While Harden-Runner offers powerful features, there are certain limitations based on the environment, such as OS support. See the complete list in [Known Limitations](docs/limitations.md).
## Testimonials
---
> _I think this is a great idea and for the threat model of build-time, an immediate network egress request monitoring makes a lot of sense_ - [Liran Tal](https://stars.github.com/profiles/lirantal/), GitHub Star, and Author of Essential Node.js Security
## Discussions
> _Harden-Runner strikes an elegant balance between ease-of-use, maintainability, and mitigation that I intend to apply to all of my 300+ npm packages. I look forward to the tool’s improvement over time_ - [Jordan Harband](https://github.com/ljharb), Open Source Maintainer
Join the conversation! For questions, ideas, or feedback, visit our [Discussions Page](https://github.com/step-security/harden-runner/discussions).
> _Harden runner from Step security is such a nice solution, it is another piece of the puzzle in helping treat the CI environment like production and solving supply chain security. I look forward to seeing it evolve._ - Cam Parry, Staff Site Reliability Engineer, Kapiche
For enterprise support, email support@stepsecurity.io. Interested in using Harden-Runner in other CI/CD platforms? Reach out to interest@stepsecurity.io.
## Workflows using harden-runner
---
Some important workflows using harden-runner:
| |Repository |Link to insights|
|--|----------|----------------|
|1.|[nvm-sh/nvm](https://github.com/nvm-sh/nvm/blob/master/.github/workflows/lint.yml)|[Link to insights](https://app.stepsecurity.io/github/nvm-sh/nvm/actions/runs/1757959262)|
|2.|[jsx-eslint/eslint-plugin-react](https://github.com/jsx-eslint/eslint-plugin-react/blob/master/.github/workflows/release.yml)|[Link to insights](https://app.stepsecurity.io/github/yannickcr/eslint-plugin-react/actions/runs/1930818585)
|3.|[microsoft/msquic](https://github.com/microsoft/msquic/blob/main/.github/workflows/docker-publish.yml)|[Link to insights](https://app.stepsecurity.io/github/microsoft/msquic/actions/runs/1759010243)
|4.|[ossf/scorecard](https://github.com/ossf/scorecard/blob/main/.github/workflows/codeql-analysis.yml)|[Link to insights](https://app.stepsecurity.io/github/ossf/scorecard/actions/runs/2006162141)
|5.|[Automattic/vip-go-mu-plugins](https://github.com/Automattic/vip-go-mu-plugins/blob/master/.github/workflows/e2e.yml)|[Link to insights](https://app.stepsecurity.io/github/Automattic/vip-go-mu-plugins/actions/runs/1758760957)
## License
## How does it work?
Harden-Runner GitHub Action downloads and installs the StepSecurity Agent.
- The code to monitor file, process, and network activity is in the Agent.
- The agent is written in Go and is open source at https://github.com/step-security/agent
- The agent's build is reproducible. You can view the steps to reproduce the build [here](http://app.stepsecurity.io/github/step-security/agent/releases/latest)
Harden-Runner is open source. See the [LICENSE](LICENSE) file for details.
description:"Security agent for GitHub-hosted runner to monitor the build process"
name:"Harden-Runner"
description:"Harden-Runner provides runtime security for GitHub-hosted and self-hosted runners"
inputs:
allowed-endpoints:
description:"Only these endpoints will be allowed if egress-policy is set to block"
@@ -17,18 +17,27 @@ inputs:
required:false
default:"false"
disable-sudo:
description:"Disable sudo access for the runner account"
description:"Disable sudo access for the runner account. Note: This parameter will be deprecated in the future. Please use disable-sudo-and-containers instead."
required:false
default:"false"
disable-sudo-and-containers:
description:"Disable sudo and container access for the runner account"
required:false
default:"false"
disable-file-monitoring:
description:"Disable file monitoring"
required:false
default:"false"
policy:
description:"Policy name to be used from the policy store"
For GitHub-hosted runners, Harden-Runner GitHub Action downloads and installs the StepSecurity Agent.
- The code to monitor file, process, and network activity is in the Agent.
- The community tier agent is open-source and can be found [here](https://github.com/step-security/agent). The enterprise tier agent is closed-source. Both agents are written in Go.
- The agent's build is reproducible. You can view the steps to reproduce the build [here](http://app.stepsecurity.io/github/step-security/agent/releases/latest)
- You can find more details in this [blog post](https://www.stepsecurity.io/blog/introducing-harden-runner-for-kubernetes-based-self-hosted-actions-runners)
- ARC Harden Runner is NOT open source.
### Self-Hosted VM Runners (e.g. on EC2)
- For self-hosted VMs, you add the Harden-Runner agent into your runner image (e.g. AMI).
- You can find more details in this [blog post](https://www.stepsecurity.io/blog/ci-cd-security-for-self-hosted-vm-runners)
* Only Ubuntu VM is supported. Windows and MacOS GitHub-hosted runners are not supported. There is a discussion about that [here](https://github.com/step-security/harden-runner/discussions/121).
* Harden-Runner is not supported when [job is run in a container](https://docs.github.com/en/actions/using-jobs/running-jobs-in-a-container) with built-in labels such as `ubuntu-latest`, as it needs sudo access on the Ubuntu VM to run. The limitation is if the entire job is run in a container. However, such jobs can be monitored when using custom VM images with GitHub-hosted runners. This is also not a limitation for Self-Hosted runners.
if(data.includes("StepSecurity Harden Runner is disabled")){
needsSubscription=true;
}
}catch(err){
//console.error(err);
}
if(needsSubscription){
awaitcore.summary
.addSeparator()
.addRaw(
`<h2>⚠️ Your GitHub Actions Runtime Security is currently disabled!</h2>`
);
awaitcore.summary
.addRaw(
`
<p>Itappearsthatyou're using the <a href="https://github.com/step-security/harden-runner">Harden-Runner GitHub Action</a> by StepSecurity within a private repository. However, runtime security is not enabled as your organization hasn'tsignedupforafreetrialorapaidsubscriptionyet.</p>
core.info(`Adding cacheHost: ${url.hostname}:443 to allowed-endpoints`);
confg.allowed_endpoints+=`${url.hostname}:443`;
}catch(exception){
// some exception has occurred.
core.info("Unable to fetch cacheURL");
if(confg.egress_policy==="block"){
core.info("Switching egress-policy to audit mode");
confg.egress_policy="audit";
letidToken: string=awaitcore.getIDToken();
letresult: PolicyResponse=awaitfetchPolicy(
context.repo.owner,
policyName,
idToken
);
confg=mergeConfigs(confg,result);
}catch(err){
core.info(`[!] ${err}`);
// Only fail the job if ID token is not available
if(err.message&&err.message.includes('Unable to get ACTIONS_ID_TOKEN_REQUEST')){
core.setFailed('Policy store requires id-token write permission as it uses OIDC to fetch the policy from StepSecurity API. Please add "id-token: write" to your job permissions.');
}else{
// Handle different HTTP status codes
if(err.statusCode>=400&&err.statusCode<500){
core.error('Policy not found');
}else{
core.error(`Unexpected error occurred: ${err}. Falling back to egress policy audit`);
Blocking a user prevents them from interacting with repositories, such as opening or commenting on pull requests or issues. Learn more about blocking a user.