Nessus is a globally recognized, industry-standardvulnerability scannerused by security professionals to identify security flaws in a network, operating system, or application. Developed by Tenable, it is a comprehensive tool that automates the process of finding weaknesses such as unpatched software, weak passwords, misconfigurations, and "zero-day" vulnerabilities.
Nessus operates by probing a target system and comparing the results against an extensive, constantly updated database of thousands of known vulnerabilities (plugins). The scanning process typically involves:
Host Discovery: Identifying which devices are active on the network.
Port Scanning: Checking for open services and identifying their versions.
Vulnerability Assessment: Running specific checks to see if those services are susceptible to known exploits.
Compliance Auditing: Ensuring that systems meet specific security standards like PCI DSS or HIPAA.
Unlike "automated hacking" tools that focus on exploitation, Nessus is adiagnostic tool. It provides detailed reports that categorize vulnerabilities by severity (Critical, High, Medium, Low) and offers specific remediation advice on how to fix the issues. In a professional penetration test, Nessus is used during the "Vulnerability Analysis" phase to provide a broad map of the target's weaknesses. This allows the tester to prioritize which flaws to attempt to exploit manually. Regular use of Nessus is a cornerstone of any proactive vulnerability management program.
