OpenVAS: Open-Source Security Scanner for Data Communications and Networking

Introduction

In today’s interconnected digital landscape, network security has become a critical concern for organizations of all sizes. The increasing sophistication of cyber threats demands robust security measures to protect sensitive data and maintain the integrity of network infrastructure. One powerful tool in the security professional’s arsenal is OpenVAS (Open Vulnerability Assessment System), a comprehensive open-source security scanner that helps identify vulnerabilities in networks and systems.

This article explores OpenVAS in depth, focusing on its applications in data communications and networking. We’ll examine its architecture, functionality, deployment scenarios, and how it integrates within broader security frameworks. Whether you’re a seasoned system administrator, a networking professional, or a security enthusiast looking to enhance your knowledge, understanding OpenVAS can significantly improve your security posture.

What is OpenVAS?

OpenVAS is a full-featured vulnerability scanner that emerged from the Nessus project when it transitioned to a proprietary model in 2005. Originally maintained by Greenbone Networks, OpenVAS has evolved into a mature, enterprise-grade security solution while remaining completely open-source and free to use.

At its core, OpenVAS is designed to detect security vulnerabilities in systems, networks, and applications. It accomplishes this through a comprehensive database of vulnerability tests (called Network Vulnerability Tests or NVTs) that are regularly updated to reflect new threats and exploits discovered in the wild.

Key Features of OpenVAS

• Comprehensive Scanning: Tests for thousands of known vulnerabilities across various platforms and services
• Regular Updates: Receives daily updates to its vulnerability database
• Detailed Reporting: Generates comprehensive reports with vulnerability details and remediation recommendations
• Scheduling Capabilities: Supports automated, scheduled scans for continuous monitoring
• Integration Options: Can be integrated with other security tools and management systems
• Web-Based Interface: Provides an intuitive interface for configuration and management
• Scalability: Can scan individual hosts or entire network ranges

OpenVAS Architecture and Components

Understanding OpenVAS requires familiarity with its modular architecture, which consists of several interconnected components:

1. OpenVAS Scanner

The scanner is the core component responsible for executing the vulnerability tests. It connects to the target systems, performs the security checks, and collects the results. The scanner operates as a daemon (service) waiting for scan requests.

2. Vulnerability Tests (NVTs)

These are the actual tests performed by the scanner to detect vulnerabilities. OpenVAS maintains a feed of over 50,000 NVTs that are continuously updated to cover new vulnerabilities. These tests are written in the NASL (Nessus Attack Scripting Language) and cover various aspects of security:

• Network service vulnerabilities
• Web application weaknesses
• Misconfigurations
• Default or weak passwords
• Outdated software versions
• Common security issues

3. OpenVAS Manager

This component coordinates the scanning process, manages scan tasks, and stores results. It communicates with the scanner to execute tests and processes the returned data. The manager also handles user access control and scheduling.

4. Greenbone Security Assistant (GSA)

GSA provides a web-based user interface that allows administrators to configure scans, view results, and generate reports. This interface makes OpenVAS accessible to users who might not be comfortable with command-line operations.

5. OpenVAS Database

All vulnerability data, scan configurations, and results are stored in a database for easy retrieval and analysis. This allows for tracking vulnerabilities over time and comparing results between scans.

Network Communication and Data Flow

In the context of data communications, understanding how OpenVAS interacts with network infrastructure is crucial. The scanner uses various protocols and techniques to communicate with target systems:

TCP/IP Communication

OpenVAS primarily uses TCP/IP for network communications, establishing connections to various ports on target systems to test for vulnerabilities. It can:

• Initiate TCP connections to detect service availability
• Send UDP packets to identify running services
• Utilize ICMP for host discovery
• Employ application-layer protocols to interact with services

Authentication Methods

The scanner supports multiple authentication methods to perform credentialed scans, which provide more thorough assessments of target systems:

• SSH for Unix/Linux systems
• SMB/CIFS for Windows environments
• Database-specific authentication for database servers
• Web application credentials for authenticated web scanning

Network Traffic Considerations

When deploying OpenVAS, system administrators should be aware of its network footprint:

1. Bandwidth Usage: Comprehensive scans can generate significant network traffic, especially when scanning large networks
2. Impact on Services: Some tests might temporarily affect the performance of scanned services
3. Firewall Interactions: Traffic from OpenVAS might be blocked by firewalls or intrusion prevention systems
4. False Positives: Network conditions can sometimes lead to false positives or negatives

Deployment Scenarios in Different Network Environments

OpenVAS can be deployed in various network topologies, each with specific considerations:

Internal Network Scanning

When deployed within an organization’s network, OpenVAS can:

• Identify internal vulnerabilities not exposed to the internet
• Detect misconfigurations in internal services
• Verify compliance with security policies
• Discover unauthorized devices or services

Example setup: An OpenVAS server installed on a dedicated machine in the management network, with access to all network segments for comprehensive scanning.

DMZ/Perimeter Scanning

For assessing externally facing systems in the Demilitarized Zone (DMZ):

• Focus on internet-facing services
• Identify vulnerabilities that external attackers could exploit
• Validate security controls on the network perimeter

Example setup: An OpenVAS instance deployed in a security segment with controlled access to the DMZ, mimicking an external perspective.

Cloud Environment Scanning

As organizations migrate to cloud platforms, OpenVAS can adapt:

• Scan cloud-hosted virtual machines and containers
• Assess cloud service configurations
• Validate network security groups and access controls

Example setup: OpenVAS deployed as a virtual appliance within the cloud environment, with appropriate permissions to scan cloud resources.

Air-gapped Networks

For highly secure or isolated networks:

• Offline deployment with manual NVT updates
• Focused scanning without external connectivity
• Customized reporting for compliance requirements

Example setup: A standalone OpenVAS installation with periodically updated vulnerability databases transferred through secure means.

Practical Implementation and Configuration

Setting up and configuring OpenVAS involves several steps that system administrators should understand:

Basic Installation Process

On a Debian/Ubuntu system, installation typically involves:

# Add repository
sudo apt-add-repository ppa:mrazavi/openvas
sudo apt update

# Install OpenVAS
sudo apt install openvas

# Initialize the NVT database
sudo openvas-setup

After installation, the setup process creates initial user accounts and downloads the latest vulnerability tests.

Scan Configuration

To configure effective scans, administrators should:

1. Define Target Systems: Specify IP addresses, ranges, or hostnames to scan
2. Select Scan Policies: Choose appropriate scan depths and test categories
3. Configure Credentials: Provide authentication details for thorough testing
4. Set Scan Schedule: Determine frequency and timing of automatic scans

Result Interpretation

Understanding scan results requires knowledge of:

• Severity Ratings: How critical each vulnerability is (High, Medium, Low)
• False Positives: Identifying and marking incorrect findings
• Remediation Priorities: Determining which issues to address first
• Trend Analysis: Tracking security improvements over time

Integration with Network Security Infrastructure

OpenVAS doesn’t operate in isolation but fits into a broader security ecosystem:

Security Information and Event Management (SIEM)

OpenVAS can feed vulnerability data to SIEM systems, enabling:

• Correlation between vulnerability data and security events
• Comprehensive security posture visualization
• Automated alerting based on vulnerability discovery

Continuous Integration/Continuous Deployment (CI/CD)

In modern DevOps environments, OpenVAS can:

• Perform automated security testing during build processes
• Block deployments with critical security issues
• Provide feedback to development teams about security flaws

Network Access Control (NAC)

Integration with NAC solutions allows:

• Dynamic access decisions based on security posture
• Quarantining of vulnerable systems
• Automated remediation workflows

Challenges and Limitations

While powerful, OpenVAS has certain limitations administrators should be aware of:

Performance Considerations

• Comprehensive scans can be resource-intensive
• Large networks may require distributed scanning architecture
• Memory and CPU requirements increase with concurrent scans

False Positives and Negatives

• Some vulnerabilities might be reported incorrectly due to network conditions
• Certain vulnerability types require additional verification
• Custom or unusual configurations might cause inaccurate results

Keeping Up with Updates

• Regular updates are essential for effective vulnerability detection
• Maintaining the system requires dedicated resources
• Air-gapped environments face challenges with timely updates

Security Best Practices for OpenVAS Deployment

To maximize effectiveness while minimizing risks:

Secure the Scanner Itself

• Keep the OpenVAS installation updated
• Limit access to the management interface
• Use strong authentication for administrator accounts
• Isolate the scanner in a security management network

Responsible Scanning

• Notify system owners before intensive scans
• Schedule scans during low-traffic periods
• Implement rate limiting to prevent service disruption
• Test scan configurations in controlled environments first

Data Protection

• Encrypt vulnerability reports and scan results
• Implement access controls for scan findings
• Develop clear data retention policies
• Consider the sensitivity of discovered vulnerabilities

Future Developments and Trends

The field of vulnerability scanning continues to evolve, with several trends influencing OpenVAS development:

Container Security

As containerization becomes mainstream, OpenVAS is adapting to:

• Scan container images for vulnerabilities
• Assess container runtime configurations
• Integrate with container orchestration platforms

Cloud-Native Security

The shift to cloud-native architectures pushes OpenVAS to evolve toward:

• API-driven scanning capabilities
• Serverless function assessment
• Cloud service configuration analysis

Automation and Orchestration

Security automation trends are influencing OpenVAS through:

• API-first approaches to scanning
• Integration with security orchestration platforms
• Automated remediation workflows

Conclusion

OpenVAS stands as a powerful, flexible, and cost-effective solution for vulnerability assessment in diverse network environments. Its open-source nature, comprehensive test database, and modular architecture make it suitable for organizations of all sizes seeking to enhance their security posture.

For system administrators and network security professionals, mastering OpenVAS provides valuable capabilities for identifying, prioritizing, and addressing security vulnerabilities before they can be exploited. As with any security tool, its effectiveness depends on proper implementation, regular updates, and integration within a broader security strategy.

By incorporating OpenVAS into their security practices, organizations can gain visibility into their vulnerabilities, make informed decisions about risk mitigation, and ultimately build more resilient network infrastructures in an increasingly threatening digital landscape.