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Best Free Alternatives to Nessus Professional (v11.x Agentic AI)
Stop paying $3,590/yr (Standard) | $3,990/yr (with Advanced Support). Discover professional-grade tools that won't break your budget.
Category: Vulnerability AssessmentVerified for 2025
Top Recommended Replacements
Greenbone Community / OpenVAS
FREETop Professional Free Alternative
Why we like it
100% free; 20+ years of development; includes 100,000+ vulnerability tests; provides a full web-based management interface; no vendor lock-in.
Keep in mind
The community feed is delayed by 14 days compared to the enterprise version; interface is significantly more complex than Nessus.
ZeroThreat AI
FREEBest for Modern Web & APIs
Why we like it
2026 breakout tool; combines DAST with automated penetration testing; AI-driven engine for zero-config scanning of APIs and microservices; agentless deployment.
Keep in mind
Newer platform with a smaller 'legacy' infrastructure plugin library compared to Tenable.
Nmap (with NSE)
FREEBest for Network Discovery
Why we like it
The global standard for port scanning; Nmap Scripting Engine (NSE) allows for deep vulnerability detection; 100% free and incredibly lightweight.
Keep in mind
No graphical interface (CLI only); requires high technical proficiency to build comprehensive vulnerability reports.
Intruder
Best for Automated Ease-of-Use
Why we like it
Cloud-native and fully automated; beautiful interface; prioritizes vulnerabilities based on what is actually 'exposed' to the internet; great for SMBs.
Keep in mind
Less granular control than Nessus; more expensive than the open-source alternatives.
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