Free and open source products cover many jobs well. The price is zero, but the cost is the time your team spends running them. So the right choice depends on what you need and who will run it.
Choose free or open source when:
- You have engineers who can deploy, set up and maintain self-hosted infrastructure
- You need transparent code for auditing or customization
- The solution is one component of a larger custom security pipeline
- You are learning, prototyping, or running ad-hoc analysis
- Compliance requirements do not mandate vendor SOC 2 or FedRAMP attestation
Choose commercial when:
- You need 24/7 vendor support with response SLAs
- Compliance frameworks require attested vendors (SOC 2, FedRAMP, HIPAA BAA)
- You would rather pay than run it yourself: managed updates, infrastructure and threat intelligence
- Your customers expect a vendor that is accountable for the product
- Your team is small and cannot maintain self-hosted security solutions
Free endpoint protection
Microsoft Defender is built into Windows 10 and 11. ClamAV is the open source choice for Linux servers and mail gateways. For a company endpoint program, compare the endpoint protection products listed here.
Best Free Vulnerability Scanners
OpenVAS is a free network vulnerability scanner. Nikto scans web servers. Nuclei runs template-based checks. OWASP ZAP does DAST. Trivy scans container images. Snyk Open Source (free tier) covers dependencies. Nmap maps the network.
Best Free OSINT Solutions
theHarvester gathers email addresses, subdomains, and host information from public sources. Maltego Community Edition supports basic graph-based OSINT investigations. Shodan free tier provides limited internet-wide host search. SpiderFoot OSINT automates reconnaissance workflows. crt.sh and the SecurityTrails free tier cover DNS and certificate transparency lookups.
Best Free SIEM and SOC Solutions
Wazuh is a free open source SIEM with HIDS, file integrity monitoring, vulnerability detection and compliance dashboards built in. ELK Stack (Elasticsearch, Logstash, Kibana) with security settings is a common base. OSSEC is the original HIDS project from which Wazuh forked. Suricata and Zeek (formerly Bro) provide network detection. For SOAR-like automation, n8n and Tines have free tiers you can try.
Best Free Password Managers and Encryption
Bitwarden Free covers personal password management and is open source. KeePass and KeePassXC are the local-first, open source alternatives. For file encryption, VeraCrypt handles full disk and container encryption. GnuPG (GPG) remains the standard for email and file encryption with public key cryptography.
Free Solutions for SaaS Startups
A SaaS startup can build a credible early-stage security program almost entirely on free solutions: Cloudflare Free for WAF and DDoS protection, Bitwarden Teams free tier for password sharing, GitHub Advanced Security free for public repos, AWS Security Hub for cloud posture, Wazuh for HIDS and basic SIEM, Snyk Open Source free for SCA, and OWASP ZAP for DAST. As you approach SOC 2 audit, expect to move to commercial solutions that produce evidence auditors accept.