Scan Your Windows and Linux Servers for Vulnerability with Nessus

In today‘s threat landscape, proactive vulnerability management is a must for securing critical systems and data. According to recent statistics, on average 4,012 website security incidents occur every day, and the global average cost of a data breach now exceeds $4 million. With attackers continuously finding new ways to exploit weaknesses, organizations need to identify and remediate vulnerabilities before they lead to costly breaches.

This is where using an automated vulnerability scanning tool like Nessus can help harden your security posture. In this comprehensive guide, we‘ll cover everything you need to know about leveraging Nessus to find and fix vulnerabilities in your Windows and Linux servers.

What is Vulnerability Scanning?

Vulnerability scanning refers to the process of proactively identifying security weaknesses in IT systems and applications. It involves using special software tools to probe networks, servers, endpoints, web apps, and other assets to uncover vulnerabilities that could be exploited by attackers.

Common vulnerabilities detected include:

Unpatched systems missing the latest security updates
Default or weak passwords that are easy to guess
Outdated software containing known vulnerabilities
Insecure system configurations
Missing security patches for known bugs
Unnecessary open ports and services
Privilege escalation flaws
Improper error handling that could lead to information leaks

By finding and addressing these security gaps before attackers discover them, organizations can drastically reduce their risk of being breached.

Why Use a Vulnerability Scanner?

There are several key reasons why every organization should be utilizing a vulnerability scanning solution as part of their security strategy:

Comprehensive Coverage – Scanners test for thousands of possible vulnerabilities and misconfigurations across an environment. IT teams would struggle to achieve the same level of coverage attempting to do it manually.

Continuous Monitoring – Scans should be run on a regular basis to detect new threats as they emerge, rather than being limited to infrequent audits.

Accuracy – Advanced scanners minimize false positives by combining vulnerability checks with contextual awareness of the environment being assessed.

Prioritization – Scanner reports highlight the most critical risks that should be fixed first based on severity andexploitability.

Compliance – Scans help satisfy vulnerability assessment requirements for regulations and compliance standards.

Efficiency – Automating scans drastically reduces the time and effort compared to manual testing.

Introducing Nessus

Nessus by Tenable is one of the most widely used and trusted vulnerability assessment platforms. Tenable has over 30,000 customers including many Fortune 500 companies and government agencies. Here‘s an overview of some key capabilities:

Broad vulnerability coverage with over 2,800 plugins tuned for accuracy
Scans networks, servers, endpoints, web apps, containers, and cloud environments
Flexible deployment options including on-premises, cloud, and portable versions
User-friendly interface and dashboards for one-click scanning and reporting
Compliance audits for standards like PCI DSS, HIPAA, NERC CIP, FISMA, and DISA STIGs
APIs and integrations with SIEM, ticketing, threat intelligence, and other security tools
Available as low-cost Nessus Essentials for small business and individual use

Nessus consistently ranks among the top vulnerability scanners in independent industry testing for its breadth of coverage, accuracy, and ease of use. It provides a cost-effective way for organizations of any size to identify and remediate security gaps before attackers can exploit them.

How Nessus Scans for Vulnerabilities

Under the hood, Nessus leverages an array of advanced techniques to detect vulnerabilities and misconfigurations across assets. Some key aspects of how it works include:

Continuously Updated Vulnerability Database – The Nessus knowledge base contains 58,000+ individual vulnerability checks tuned for accuracy based on real-world testing and community feedback. New updates are released multiple times per week.

Authenticating Scans – For deeper scanning, Nessus can log into assets using provided credentials. This allows more thorough checks dependent on system access.

Passive Traffic Analysis – Nessus can passively monitor network traffic for security events and protocol anomalies indicating potential issues.

Configuration Auditing – System configurations are checked against security best practices and known hardening guides like CIS Benchmarks.

Vulnerability Validation – Findings are verified using exploit code, where possible, to avoid false positives from misinterpreted scan results.

Threat Intelligence – New vulnerability testing is added based on emerging threat research from Tenable‘s elite team of security experts.

The combination of these techniques allows Nessus to deliver comprehensive coverage with maximum accuracy to avoid wasting time chasing down false alarms.

Key Features of Nessus

Nessus provides an extensive set of capabilities to meet the needs of security practitioners across various use cases:

Broad Assessment Coverage

Nessus scans assess all types of assets including networks, servers, endpoints, embedded systems, IoT devices, virtual environments, containers, Kubernetes, cloud infrastructure, SCADA systems, web applications, and more.

Intuitive User Interface

The web-based UI provides one-click vulnerability scanning, customizable dashboards, and graphical reporting for easy use. Role-based access control manages permissions.

Flexible Deployment Options

Nessus can be deployed on-premises, via cloud-based Nessus Manager, or through Tenable.io. The agent-based option allows decentralized scanning across distributed environments. Portable versions are available for remote field use.

Compliance Audits and Templates

Pre-built assessment templates allow continuous compliance monitoring for standards like PCI DSS, HIPAA, CIS Benchmarks, DISA STIGs, and more.

Integration and Automation

APIs and webhooks allow integrating scan results with tools like Security Information and Event Management (SIEM), ticketing systems, threat intel platforms, and more. Scans can also be automated via scheduler or CI/CD pipelines.

Custom Assessment Creation

Flexible policies allow customizing scans tailored to specific assets and objectives beyond out-of-the-box templates. Unique plugins can also be developed using NASL and other languages.

Live Results and Real-Time Dashboards

Live Results provide a real-time view into findings as scans run. Dashboards track trends across scans enabling prioritization of most critical vulnerabilities.

Actionable Reporting

Custom reports can be generated with executive and technical summaries of vulnerabilities, compliance gaps, and security posture across the environment. Reports can be exported, shared with stakeholders, and incorporated into presentations.

These capabilities make Nessus a versatile tool that can be leveraged across a wide variety of vulnerability management use cases.

Scanning Windows Servers

Protecting Windows servers is a top priority since they often host sensitive data assets and valuable IT services. Nessus can assess Windows machine securely using remote scanning and local credentialed scans.

For broad vulnerability coverage, the "Basic Network Scan" template is a good starting point. It includes checks for missing OS and application patches, insecure configurations, default accounts/passwords, vulnerable services, user privilege issues, and more.

Remote vs. Credentialed Scanning

Uncredentialed remote scans provide a quick overview of externally facing vulnerabilities but are limited in visibility. For deeper scanning:

Use a domain admin or dedicated scanner account with local admin rights
Enable relevant administrative shares like C$, D$, etc.
Supply credentials in scan settings for local logins

This allows more thorough checks for missing patches, configuration risks, privilege escalation flaws, and other issues requiring system access.

Tuning Scan Settings

Default scan settings balance depth and speed but can be adjusted as needed:

Select stealth options to avoid interference with production activities
Target specific vulnerabilities or compliance checks to focus on priority risks
Adjust depth of file system inspection, registry scanning, and service checks as needed
Schedule periodic scans using a recorded template for consistency

Automating Server Scans

Ongoing scans should be scheduled continuously versus intermittent scanning:

Use built-in scheduler to run scans on a recurring basis
Trigger scans via scripting, batch jobs, or CI/CD pipeline tools
Centrally launch and manage scans using Nessus Manager or Tenable.io

Regular automated scans provide continuous monitoring to detect new vulnerabilities in Windows servers as they emerge.

Scanning Linux Servers

Nessus is equally adept at assessing Linux systems like Red Hat, CentOS, Debian, Ubuntu, SUSE and more. The "Basic Network Scan" template provides broad coverage, and credentials can be supplied for local logins.

Unique Linux Checks

In addition to common scans, Nessus includes Linux-specific checks like:

Verifying OS kernel, distro, and package patch levels
Checking for vulnerable SUID/GUID files
Detecting weak permissions on system files and directories
Auditing configuration of sshd, crond, syslog and other daemons
Identifying risks with containers, Kubernetes, and microservices
Finding issues in shared libraries and interpreters

Credentialed vs. Uncredentialed

Similar to Windows, authenticated scanning using an admin account yields more thorough results by enabling additional checks requiring deeper system access.

Customizing Linux Scans

Fine tuning may be needed to maximize efficiency and accuracy:

Target scans to specific services like Apache/Nginx web servers
Adjust depth of file analysis based on performance impact
Enable Anti-Evasion settings to detect attempts to block scanning
Suppress noisy false positives using plugin modifications

Automating and Scheduling

Ongoing scans should be scheduled to provide continuous automated monitoring of Linux systems:

Use Nessus scan templates to ensure consistency
Integrate scanning into CI/CD deployment pipelines
Centrally launch and manage scans using Nessus Manager

Frequent automated vulnerability scans of Linux servers is key to identifying newly introduced risks before they can be exploited.

Scanning Containers

Containers and orchestrators like Docker and Kubernetes introduce new risks if not properly secured. Nessus can help identify misconfigurations and vulnerabilities in these environments.

Key aspects of container scanning include:

Assessing host kernel and orchestrator vulnerabilities
Scanning running container images for known vulnerabilities
Checking container configurations against security best practices
Testing secrets management, network policies, and access controls
Identifying risks from overprivileged containers
Monitoring hosts and containers for malicious activity

Since container lifecycles are ephemeral, periodic scanning is critical to detecting risks as environments evolve. Nessus integrates with CI/CD pipelines for automated scanning triggered by new deployments.

Scanning for Web Vulnerabilities

Nessus Web Application Scanning provides deep insight into risks within web apps and APIs. Key capabilities:

Crawl sites to discover all pages, forms, scripts, and assets
Audit server configs for flaws like information leaks
Test authentication and session management
Detect XSS, SQLi, command injection, and other common vulnerabilities
Identify insecure files and directories
Check for weak cryptography like SSL issues
Assess compliance with standards like OWASP Top 10

Web app scanning can help developers and security teams identify and remediate vulnerabilities introduced during rapid agile development cycles.

Scanning Cloud Infrastructure

Scanning cloud environments requires safely assessing infrastructure-as-a-service (IaaS) and platform-as-a-service (PaaS) components:

IaaS Scanning:

Audit cloud server VMs using standard scans
Check virtual network devices and firewalls
Identify misconfigurations of storage buckets
Assess hardening of base images

PaaS Scanning

Scan cloud-based web apps and APIs
Analyze serverless code for vulnerabilities
Audit the security of managed services like databases
Check policies and compliance reporting

Proper configuration is critical for securing cloud environments against threats.

Use Cases for Nessus

Nessus provides versatile scanning capabilities applicable across many different functions within an organization:

Security Teams – Continuous vulnerability monitoring to detect risk and compliance gaps across environments. Prioritize remediation based on potential business impact.

Penetration Testers – Leverage Nessus to efficiently identify a broad set of vulnerabilities as a precursor to manual pen testing.

MSSPs / MDRs – Offer vulnerability scanning-as-a-service to clients as a managed service. Provide ongoing monitoring rather than point-in-time audits.

Compliance Groups – Use predefined compliance templates to automate audits for standards like PCI DSS, HIPAA, FISMA/NIST, etc.

IT / System Admins – Scan servers, endpoints, and infrastructure to identify and patch vulnerabilities.

Cloud Teams – Assess risks of IaaS and PaaS services used. Monitor container hosts and images.

Developers – Integrate scanning into CI/CD pipeline for DevSecOps.

M&A Due Diligence – Assess security risks and posture of companies being acquired or merged with.

Universities – Provide hands-on vulnerability assessment experience for cybersecurity students to build skills.

These examples demonstrate the versatile value Nessus delivers across IT and InfoSec roles.

Best Practices for Effective Vulnerability Management

To build an effective vulnerability management program, organizations should consider these best practices:

Maintain a continuously updated asset inventory to track all hardware and software.
Schedule scans frequently such as weekly or daily to identify new threats.
Tune scans to maximize coverage while minimizing false positives and performance impact.
Validate findings manually via pen testing or attack simulation.
Prioritize remediation based on severity, compliance risk, and potential impact.
Track vulnerability metrics over time and report to key stakeholders.
Foster collaboration between security, IT, cloud, and development teams.
Correlate findings with threat intel to focus on active risks.
Automate scanning and integrate results into SIEM, ticketing, and workflows.

Ongoing management is key to ensure vulnerability scanning translates into meaningful risk reduction rather than just generating reports.

Pricing Overview

Nessus offers economical pricing suitable for organizations of all sizes:

Nessus Essentials – Free version for personal and educational use. Scans up to 16 IPs.

Nessus Professional – For commercial scanning by individuals. Subscription based on number of IPs scanned.

Nessus Expert – For larger internal vulnerability assessment programs. Licensed by number of concurrent scans.

Tenable.io – Cloud-based scanning and management platform. Tiered subscription plans based on assets monitored.

Nessus Premium – Highest level capabilities. Licensed by number of IPs.

Free trials are available to evaluate capabilities before purchasing. Volume licensing discounts provide better pricing for larger organizations.

Conclusion

Regular vulnerability scanning with a tool like Nessus should be a foundational component of every organization‘s security strategy. Nessus provides a cost-effective way for enterprises of any size to identify and prioritize vulnerabilities across diverse environments before cybercriminals have a chance to exploit them.

By leveraging its broad vulnerability coverage, accuracy, and intuitive workflow, IT and security teams can continuously monitor assets for emerging risks, meet compliance requirements, and harden attack surfaces. Integrating Nessus-based vulnerability management into your security program is one of the most impactful steps you can take to proactively protect your organization from threats.