What is network scanning?

A network scanner discovers all the devices, applications and services connected to your network. Without it, you have no clear view of what you’re protecting.

When you scan a network, the scanner sends signals — called probes — to devices and waits for responses. 

From that data, it identifies things like:

• Which devices are active
• Operating systems and services they’re running
• Which ports are open or closed
• Installed software versions

This information helps you spot cyber exposures before attackers do. You'll know if a server runs outdated software or if you have an unnecessary service with an open port.

Your network changes all the time. New devices connect, cloud workloads spin up and users add shadow IT without telling anyone. 

If you don’t actively scan your attack surface, you leave blind spots open for attackers.

Here’s why you need it:

• Scanning reveals unmanaged devices like personal laptops, rogue wireless access points or forgotten servers.
• Attackers often scan for open ports to find easy entry points. You can close those doors first.
• A scan tells you if you’re missing critical patches or security settings are weak.
• Support compliance requirements like PCI DSS, which mandates regular internal and external vulnerability scans, and HIPAA, which requires continuous risk analysis to protect electronic patient health information.
• With a clear network map, you can remove unused services, segment networks and harden critical assets.

Without regular scanning, you’re leaving your network security up to chance.

When you start a network scan, the scanner doesn't just blast packets randomly. It uses a systematic approach to find devices. 

Here's how to scan a network for vulnerabilities:

• Discovery: The scanner checks which IP addresses respond. It uses techniques like ping sweeps, ARP requests or DNS lookups to find live hosts.
• OS fingerprinting: It analyzes responses to identify operating systems, running services, software versions and other details.
• Device enumeration: It digs deeper into open ports, probing services like HTTP, SSH or SMB to gather configuration information.
• Reporting: It compiles the results into a network inventory map detailing devices, services and potential vulnerabilities.

Active vs. passive network scanning

Conduct an active scan by sending signals to see which devices respond. The downside is it creates extra traffic on your network, so you'll want to plan for it and maybe do it during off-hours.

Do a passive scan, which just listens to the traffic that's already happening on your network. 

It works great when dealing with sensitive systems like factory equipment or hospital networks, where you can't risk disruptions. The catch is that quiet devices might slip by unnoticed.

For the most visibility, combine both approaches.

Not all scans serve the same purpose. You’ll often use different scan types together for a holistic picture.

Host discovery scans

These scans answer a simple question: “What’s alive on this network?” They use ping sweeps or ARP requests to find devices, even those you didn’t know were there.

Port scanning

Once you know a host is live, you scan its ports. Open ports mean services are listening. That could be a web server on port 80 or a database on 3306. Port scans help you find unnecessary or insecure services. Attackers use this technique for reconnaissance. You should, too.

Vulnerability scans

Vulnerability scanning goes deeper than ports. They look for missing patches, outdated software, weak configurations and known CVEs. You can run:

• Authenticated scans: Log in with credentials to fully view software versions and security settings.
• Unauthenticated scans: Scan from the outside, like an attacker would, to find exposures.

Each scan gives you another layer of detail about your network.

Network scanning tools vary, from simple discovery utilities to comprehensive vulnerability management solutions. Understanding the options helps you choose what fits your security needs.

• Basic discovery tools help you quickly find devices, open ports, hosts and services running on your network. They're great for getting that initial overview, though they won't dig deep into actual vulnerabilities.
• Open-source vulnerability scanners check for known security issues and configuration problems. You get functionality without the extra expenses.
• Enterprise-grade scanners give you comprehensive coverage with reliable vulnerability detection, ongoing monitoring and smooth integration options. These help you figure out which risks to tackle first and work well with your existing security setup.
• Cloud-based scanning platforms are flexible solutions that can handle dynamic, spread-out environments. Perfect if you're managing large or mixed infrastructures.

When you need ongoing, accurate vulnerability assessment across both on-prem and cloud systems, pick a scanner that integrates with your current cybersecurity tools and risk management approach.

Want a robust, integrated network scanning solution that grows with your environment? See how Tenable Vulnerability Management delivers complete visibility and practical vulnerability insights to keep you ahead of cyber threats.

Understanding the difference between network scanning and vulnerability scanning is key to finding cyber exposures and securing your vast attack surface. 

Network scanning acts like a detailed attendance check. It discovers every device, service and open port on your network, including unauthorized or unmanaged assets. 

Vulnerability scanning then inspects those devices to identify missing patches, outdated software, misconfigurations and known security flaws.

Together, these scans give you:

• A comprehensive, up-to-date inventory of all assets on your network
• Vulnerability insight, so you know which exposures pose the greatest risk based on your unique environment
• The ability to detect and prioritize threats before attackers can exploit them

Network scanning provides the foundation for vulnerability scanning, ensuring you don’t overlook any device or service. Plus, combining unauthenticated scans (view from outside) with authenticated scans (inside system access) delivers a fuller, more accurate security picture.

To get the most out of both, follow best practices like:

• Run vulnerability scans using your inventory to ensure you cover everything attackers might target.
• Focus your remediation on the most critical issues using risk-based prioritization.
• Set up automated scans and alerts to maintain ongoing coverage without manual work.
• Tailor your scanning policies to match different device types and network areas.
• Connect scan results with your existing security tools to speed up incident response.
• Train your teams on how to read scan data and collaborate on fixes.
• Keep updating your scanning approach as your network and threat landscape change.

By combining network scanning and vulnerability scanning strategically, you gain full visibility and actionable intelligence, empowering your security team to reduce risk and strengthen defenses.

Follow the link for a deeper dive into network scanning vs. vulnerability scanning.

Your network isn’t just a set of on-prem servers anymore. It’s hybrid cloud workloads, remote endpoints and operational technology (OT). 

Network scanning ties it all together by giving you a live inventory.

It’s also part of a zero-trust strategy. You limit an attack's blast radius by continuously verifying what’s on your network and how it behaves.

Specifically, scanning gives you comprehensive and continuous asset visibility, a prerequisite for a never trust, always verify model.

Scanning feeds the data you need to measure and reduce exposure over time in exposure management. Modern platforms even combine network scanning with container security, infrastructure as code scanning and CI/CD integrations so you can secure everything from development to production.

Tenable Research, for example, has, to date, has published more than 257,000 plugins, covering more than 101,731 CVE IDs.

Network scanning plays a critical role in vulnerability management. It’s the foundation for identifying where your risks exist. 

Vulnerability management relies on accurate, up-to-date information about every device, application and service on your network. That’s why network scanning must go beyond simple discovery and port checks to include deep inspection and detailed vulnerability detection.

Network scanners use active and credentialed scans for vulnerability management. Active scans probe devices directly to detect open ports and running services. Credentialed scans log into systems to analyze software versions, configurations and patch levels. This approach uncovers hidden vulnerabilities that external scans alone would miss.

Vulnerability management then layers risk scoring onto these scan results to help you prioritize remediation. 

Instead of chasing every alert, you focus on vulnerabilities put your business at risk.

When you combine scanning data with vulnerability intelligence, you'll catch emerging threats faster.

Network scanning feeds into vulnerability management and gives you the raw data to find cyber exposures and track how they change. 

Without scanning, you won't have visibility or context to reduce your cyber risk.

Exposure management expands on vulnerability management by focusing on individual weaknesses and your entire attack surface. 

Network scanning is essential here because it gives you the live inventory of assets and connections that define your digital footprint.

Comprehensive exposure management requires continuous network scanning that discovers on-prem devices, cloud workloads, virtual machines, OT and transient or mobile assets. This full-spectrum visibility uncovers shadow IT and unmanaged devices that often slip through the cracks.

Beyond discovery, exposure management integrates scan data with risk scoring and threat intelligence to highlight vulnerable parts of your threat actors might use as targeted attack paths. It helps you see how vulnerabilities relate and where an attacker might move laterally across your systems.

By continuously monitoring and assessing your attack surface, exposure management helps you prioritize remediation actions that reduce your overall risk. It supports compliance by providing evidence of ongoing asset discovery and vulnerability monitoring across your entire environment.

Network scanning, therefore, acts as the eyes and ears of exposure management. It delivers real-time insight that fuels risk-based decisions and aligns your security posture with the evolving threat landscape.

Network scanning helps you find devices, open ports and vulnerabilities before threat actors get to them.

Some solid network scanning practices:

• Schedule scans when your network isn't busy.
• Combine active and passive scanning to catch everything.
• Run credentialed scans for a complete picture of your systems and patches.

When you prioritize vulnerabilities by actual risk and keep your asset inventory current, you'll focus on what matters instead of chasing random vulnerability scores that don't tell the whole story.

When you prioritize vulnerabilities by actual risk and keep your asset inventory current, you'll focus on what matters instead of chasing static vulnerability scores that don't tell the whole story.

Integrating scanning with your broader cybersecurity programs, customizing scan policies for different environments and training your team to interpret scan data can maximize effectiveness. 

Automation and alerting speed up detection and remediation while reducing manual tasks. 

Want to know more about best practices? Check out our in-depth network scanner best practices page.

When considering a network scanner tool, look for a solution that has advanced features like:

Vulnerability detection to find missing patches, old software and configuration problems.

Credentialed scanning that uses login credentials to dig deeper into your systems.

Risk-based prioritization and customizable reporting so you can zero in on what matters most and show stakeholders real impact.

• Make sure the tool can grow with your organization:
• Scalability to handle bigger networks without slowing down.
• Compliance support for all the regulations you have to meet.
• Easy integration with your current security tools so everything works together.

Explore our detailed How to Select a Network Scanning Tool cluster page for a comprehensive guide on selecting the best network scanning tool for your needs.

Basic network scanners stop at discovery. They tell you what’s on your network but don’t help you understand risk or prioritize what to fix. 

Tenable goes further.

With Tenable, you can:

• Discover every asset for on-prem, cloud, OT and even transient BYOD devices.
• Run credentialed network scanning to get deeper insight into software versions, misconfigurations and missing patches.
• Passively monitor traffic to spot vulnerabilities and blind spots without disrupting sensitive systems like medical devices or industrial control systems (ICS).
• Detect threats in real time with continuous plugin updates to identify new CVEs as soon as they emerge.
• Prioritize remediation using Tenable risk scoring to fix what matters most instead of drowning in alerts.
• Stay compliant with built-in templates to make reporting easier.

Tenable also integrates passive scanning into broader vulnerability management, giving you a single view of your entire attack surface.

Tenable doesn’t just tell you what’s connected. It tells you which vulnerabilities attackers will target first, so you can fix them before they become problematic.

See how Tenable Vulnerability Management uncovers hidden network risks.

We've compiled the the most frequently asked questions about network scanning, providing answers to help with examples, hacking, and other important factors:

What are examples of network scanners?

Tenable Nessus is an example of a network scanner widely used for discovery and vulnerability assessment.

Can hackers use network scanning?

Yes. Attackers use the same scanning techniques to map your network and find weak points. That’s why you need to scan before they do.

Does network scanning affect performance?

Active scans can cause brief network noise. Passive scans have no impact because they just listen to traffic.

How often should you scan your network?

Ideally, you should continuously scan your network. At a minimum, scan weekly to catch new devices and vulnerabilities, but consistently enough to meet your compliance requirements.

What’s the difference between network scanning and network monitoring?

Scanning actively probes devices to find vulnerabilities. Monitoring passively observes traffic to detect issues over time.

How does network scanning work in a hybrid cloud environment?

In a hybrid cloud, scanners combine active probes, passive monitoring and cloud API integrations to find on-prem, cloud and virtual assets. This ensures full visibility, even for short-lived resources like containers or virtual machines.

Want a clearer view of your entire attack surface? Start with a network scan that shows you every asset, every open port and every vulnerability. See how Tenable Vulnerability Management helps you discover and reduce network risk today.