Tenable

Nessus is the tool you run to find out what is wrong with your infrastructure before someone else does. It scans machines, services and configurations, then hands you a list of flaws ranked by severity.

The Tenable store sells licences directly: you pick the term, you pay, you download. No sales cycle to sit through.

• Nessus Professional: unlimited scans, over 450 preconfigured templates, compliance audits. $4,790 for one year, $9,330.95 for two, $13,637.54 for three.
• Nessus Expert: everything in Professional, plus web application scanning and external attack surface discovery. $6,790 for one year.
• Tenable Vulnerability Management: the cloud version with continuous asset tracking, starting at $3,700 a year for 100 assets, and up to 250 assets purchasable online.
• Flaw prioritisation: EPSS, CVSS and Tenable's own VPR scores to sort out what needs fixing first.
• Add-ons: 24/7 advanced support at $400 a year, and the Nessus Fundamentals video course at $275.

Who it fits: cybersecurity consultants, penetration testers, network admins at small and mid-sized companies, and students who want to learn on the industry's reference tool.

Worth noting: this is a serious budget for a solo operator. Tenable also offers Nessus Essentials, a free version limited to 16 IP addresses, enough to test how it works before paying.