Open-Source CSPM Tools: Free Cloud Security Posture Scanners
A fair, factual roundup of the open-source CSPM tools teams use to audit cloud security posture for free — Prowler, ScoutSuite, CloudSploit, Cloud Custodian and Steampipe/Powerpipe — plus Trivy and Checkov for infrastructure-as-code. It explains briefly what CSPM is, what each tool does and which clouds it covers, where open-source point scanners end and a commercial CNAPP begins, and how PlayCISO's free self-assessment fits alongside them.
Open-source CSPM in plain words
- CSPM (cloud security posture management) is the continuous practice of finding and fixing misconfigurations and compliance gaps in your cloud accounts — public storage, over-permissive IAM, open security groups, missing logs. Several mature open-source tools do this for free.
- The most widely used open-source cloud-audit tools are Prowler, ScoutSuite, CloudSploit, Cloud Custodian and the Steampipe/Powerpipe stack. Each scans live cloud configuration against best-practice checks and reports where you deviate; none charges a licence fee for the open-source edition.
- For catching misconfigurations before they ship — in Terraform, CloudFormation and Kubernetes manifests — Trivy and Checkov are the common open-source infrastructure-as-code (IaC) scanners, complementing the live-account tools above.
- Open-source CSPM tools are point scanners: each produces a list of findings for the accounts you point it at. They do not, on their own, correlate posture with workload risk, identities and data into prioritised attack paths — that correlation is the job of a commercial CNAPP (Cloud-Native Application Protection Platform).
- If you want a fast read on where your posture stands before you set up any scanner, PlayCISO’s free, no-signup CSPM Readiness Scorecard is a weighted self-assessment across the eight domains these tools evaluate — it runs entirely in your browser and makes no cloud connection.
What CSPM is, briefly
Cloud security posture management (CSPM) is the continuous practice of finding and fixing misconfigurations and compliance gaps across your cloud accounts — public storage buckets, over-permissive IAM roles, security groups open to the internet, unencrypted data, disabled audit logging. CSPM tools read your cloud configuration, compare it against best-practice benchmarks such as the CIS benchmarks, and flag where you deviate. It is the configuration-posture layer of cloud security; for how it sits alongside workload protection, identity analysis and the rest, see the CNAPP explainer.
Open-source CSPM and cloud-audit tools
These are established open-source tools that scan live cloud accounts for misconfigurations. They are described factually below — what each does, which clouds it covers and its open-source status. Which one fits depends on your clouds and whether you want a report, a scriptable CLI or policy-as-code; evaluate against your own environment rather than any ranking:
Prowler
A command-line security assessment tool that runs hundreds of checks against your cloud accounts and maps findings to compliance frameworks such as the CIS benchmarks, PCI DSS and others. Started as an AWS CIS auditor and is now multi-cloud. Good when you want scriptable, scheduled scans and broad compliance mapping.
ScoutSuite
A read-only multi-cloud auditing tool that collects configuration data and produces a browsable HTML report highlighting risky settings by service. Well suited to a point-in-time posture review you can hand to stakeholders, rather than continuous monitoring.
CloudSploit
A misconfiguration scanner that checks cloud accounts against a library of security best-practice tests and reports failures. Multi-cloud, with a commercial scanning service also offered by Aqua on top of the open-source engine.
Cloud Custodian
A policy-as-code engine: you define rules in YAML and it can report on, tag, notify about or actively remediate cloud resources that break them. More of a governance and enforcement tool than a pure scanner — useful when you want posture rules enforced automatically, not just listed.
Steampipe / Powerpipe
Steampipe lets you query live cloud configuration with SQL; Powerpipe runs pre-built benchmarks and dashboards on top of it, including CIS and other compliance mods. A flexible option when you want to ask ad-hoc posture questions or build custom posture dashboards.
Catching misconfigurations before they ship: Trivy and Checkov
The tools above scan cloud accounts that already exist. A complementary open-source layer scans infrastructure-as-code so a misconfiguration is caught in a pull request rather than discovered later in a live account. Checkov (maintained by the team behind Prisma Cloud) is a static-analysis scanner for Terraform, CloudFormation, Kubernetes manifests, ARM, Helm and more. Trivy (maintained by Aqua Security) is a broad open-source scanner that covers IaC misconfigurations alongside vulnerabilities in container images, filesystems and repositories. Both are free and open source, and are commonly run in CI/CD next to a live-account CSPM scan.
Where open-source scanners end and CNAPP begins
Open-source CSPM tools are point scanners: each produces a list of findings for the accounts you point it at. That is genuinely valuable, and for a modest estate or a periodic audit it can be all you need. What they do not do on their own is correlate — join a misconfiguration to the exposed workload it affects, the over-permissioned identity that can reach it and the sensitive data behind it, then rank the combination by real exposure. They also leave you to own scheduling, history, de-duplication, ticketing and SIEM integration, and keeping the check coverage current.
That correlation and managed-platform layer is the job of a commercial CNAPP (Cloud-Native Application Protection Platform), which consolidates CSPM with workload protection (CWPP), identity and entitlement analysis (CIEM), IaC scanning and container/Kubernetes security into one risk view. If you are weighing open-source point tools against a platform, the CNAPP explainer walks through the pillars and what to evaluate.
A fast, free way to see your posture gaps first
Before you set up any scanner, it helps to know roughly where you stand. PlayCISO's free CSPM Readiness Scorecard is a weighted self-assessment across the same eight domains these tools evaluate — identity and access, data protection, network, logging and detection, vulnerability and patching, secrets, config and compliance, and incident-response readiness. It is deliberately not a scanner: it makes no cloud connection and runs entirely in your browser, turning your answers into a transparent 0–100 score, a per-domain breakdown and a prioritised list of gaps to fix first. Think of it as a complement to the open-source tools above — a two-minute read on where to focus, which you can then confirm by running a real scan with Prowler, ScoutSuite or one of the others.
PlayCISO's other free, no-signup tools target specific misconfigurations the scanners flag: the IAM policy analyzer surfaces over-permissioned access, the S3 bucket policy auditor checks for public-storage exposure, and the security group auditor checks for over-open network rules. See all PlayCISO tools for the full index.
Note: tool capabilities, cloud coverage and licensing change over time, and several of these projects also have commercial editions. Treat this page as a neutral starting point and confirm current details and the specific services you run against each project's own documentation before you rely on it.
Frequently asked questions
What is the best open-source CSPM tool?
There is no single best one — it depends on your clouds and how you want to run it. Prowler is a popular, broadly scoped command-line scanner for AWS, Azure, GCP and Kubernetes with a large set of compliance mappings. ScoutSuite produces an easy-to-read HTML risk report across several clouds and is good for a point-in-time review. CloudSploit focuses on misconfiguration detection across multiple providers. Cloud Custodian is a policy-as-code engine that can also report on and remediate resources. Steampipe with Powerpipe lets you query cloud configuration with SQL and run posture benchmarks (including CIS) as dashboards. Try the one that matches the clouds you run and whether you want a report, a CLI or policy-as-code; all are free to use.
Are open-source CSPM tools free to use?
Yes. Prowler, ScoutSuite, CloudSploit, Cloud Custodian, Steampipe, Powerpipe, Trivy and Checkov are all open-source projects you can run at no licence cost. Several are maintained by vendors that also sell a commercial, hosted or enterprise edition — for example Prowler has a hosted Prowler Cloud, CloudSploit and Trivy are maintained by Aqua Security, Steampipe and Powerpipe come from Turbot, and Checkov is maintained by the team behind Prisma Cloud — but the open-source command-line tools themselves are free. Your real cost is the engineering time to run, tune and triage them, and the compute they run on.
What is the difference between CSPM and an open-source cloud scanner like Prowler?
They overlap heavily. CSPM describes the capability — continuously assessing cloud configuration against best-practice and compliance benchmarks and flagging misconfigurations. An open-source tool like Prowler or ScoutSuite is one way to get that capability: you run it against your accounts and it produces the findings. The practical difference between an open-source scanner and a commercial CSPM or CNAPP platform is usually continuous scheduling, a managed dashboard and history, ticketing and SIEM integrations, broader service coverage kept up to date, and — in a CNAPP — correlation of posture findings with workload, identity and data risk. The open-source tools give you the core scan; the commercial products wrap it in a managed platform.
Do open-source CSPM tools cover AWS, Azure and GCP?
Several do. Prowler, ScoutSuite and CloudSploit are multi-cloud and support AWS, Azure and GCP (ScoutSuite and CloudSploit add further providers such as Oracle Cloud and Alibaba Cloud; Prowler also covers Kubernetes). Cloud Custodian supports AWS, Azure and GCP. Steampipe has plugins for all three and many other services, and Powerpipe runs benchmarks on top. Coverage depth varies by provider and by how current the project is, so check that the specific services you run are supported before you rely on a tool, rather than assuming parity across clouds.
Is an open-source CSPM tool enough, or do I need a CNAPP?
For a small estate, a periodic audit, or a team that can own the tooling, open-source scanners can be plenty — they find the same classes of misconfiguration a commercial CSPM looks for, at no licence cost. The case for a commercial CSPM or a CNAPP grows with scale and the need to correlate signals: a CNAPP consolidates posture (CSPM) with workload protection (CWPP), identity and entitlement analysis (CIEM), IaC scanning and container/Kubernetes security, and links those into prioritised attack paths rather than leaving you to join the findings yourself. A reasonable path is to start with an open-source scanner plus a quick self-assessment to understand your gaps, then evaluate a platform when the integration and correlation burden outweighs the licence cost. See the CNAPP explainer for how the pieces fit together.