Network scanner best practices

Network scanning is an essential tool for securing your attack surface. It helps you discover devices, open ports, vulnerabilities and misconfigurations that could be entry points for attackers. 

Without frequent and thorough scans, you risk missing new threats, unauthorized devices or outdated software with exploitable flaws.

However, if done incorrectly, a network scan can cause disruptions like network slowdowns or trigger false alarms that waste your team’s time. 

Here are some network scanning best practices to consider:

Set up regular scans to find new devices and vulnerabilities as soon as they show up on your network. 

Continuous monitoring stops attackers from taking exploiting of unknown or overlooked exposures.

Set your scans to run automatically during quiet times, like nights or weekends, when your organization might not use the network as much to avoid slowdowns or business disruptions. 

In some instances, scanning a busy database during work hours could make apps crawl or frustrate users.

How often you scan depends on asset criticality, risk tolerance and compliance requirements. 

As a baseline:

• External, internet-facing systems: Scan at least weekly since they’re most exposed.
• Internal production servers: Perform authenticated scans weekly or biweekly.
• Endpoints and user devices: Scan monthly or as part of routine patch cycles.
• Compliance mandates: Follow required schedules, such as quarterly external scans for PCI DSS.

For highly dynamic environments, like cloud workloads or containers, move toward continuous scanning. Network scanning tools can monitor assets in near real-time for instant visibility as new vulnerabilities emerge.

A comprehensive scanning strategy uses two complementary methods: active and passive scanning.

Active scanning sends probes to devices to identify open ports, services and vulnerabilities. 

While it gives you deep insights, it can occasionally disrupt sensitive systems. 

For example, aggressive scans can sometimes cause legacy printers, VoIP phones or fragile OT equipment to crash or behave unpredictably.

Pair active scanning with passive scanning to avoid these disruptions and get total visibility. This method continuously listens to network traffic to identify assets and vulnerabilities without directly interacting with devices. 

Passive scanning is especially valuable for detecting transient devices (like guest laptops) and shadow IT (unauthorized software and hardware) that scheduled active scans often miss.

Using both gives you a complete, real-time picture of your network, so you can spot known and emerging threats without interfering with critical operations.

Network scanners use two types of scans: unauthenticated (from the outside, like an attacker) and authenticated (credentialed). 

For the most accurate results, you need authenticated scanning. By logging into systems with valid credentials, the scanner can collect detailed information about installed software, patch status and local configuration settings.

This deeper look finds vulnerabilities you can't see from the outside, like missing patches or risky software settings. It also cuts down on false alerts by directly checking systems.

While credentialed scanning requires you to manage credentials, you can do this safely using a secure vault to store service accounts with read-only or minimum necessary privileges on the target systems.

A raw scan report can be overwhelming. 

To focus on actual risk, prioritize remediation using a modern, data-driven approach that moves beyond severity to include threat intelligence and business context.

First, use the Common Vulnerability Scoring System (CVSS) to understand the intrinsic severity of a vulnerability. A high CVSS score (7.0-10.0) indicates a potentially damaging flaw that you should take seriously.

Next, layer on the Exploit Prediction Scoring System (EPSS). EPSS gives you a probability score (0-100%) about a threat actor's likelihood of exploiting a vulnerability in the wild in the next 30 days. This helps you distinguish between a severe vulnerability that no one is attacking and a clear and present danger.

Finally, factor in the importance of the asset. A vulnerability with a high CVSS and high EPSS score on an internet-facing, critical production database is your absolute top priority. You can address the same vulnerability on an isolated test machine later.

To put this prioritization theory into practice, modern vulnerability management platforms use your network scan results as the foundation for a deeper, AI-driven analysis. 

For example, a platform like Tenable ingests your scanner's findings and applies its predictive Vulnerability Priority Rating (VPR) to identify which discovered vulnerabilities bad actors are most likely to exploit. 

To add crucial business context, it then layers on an asset criticality rating (ACR) for 

scanned assets. 

The most advanced systems even use this combined data to map potential attack paths, showing how a low-risk finding on one machine could compromise a critical asset elsewhere.

This approach transforms the raw output from your network scanner into a prioritized, actionable plan.

Your vulnerability scans are only as good as your understanding of what’s on your network. Attackers often exploit rogue or unmanaged devices that slip under the radar. Keeping an accurate, continuously updated asset inventory is crucial for effective security.

Use your network scanning tools to detect new devices automatically, so you always know what’s connected. This is especially important in environments where devices are frequently added, removed or moved, like offices with BYOD policies or cloud and hybrid networks.

A current asset inventory also supports compliance reporting and incident response, making tracking, containing and remedying threats easier.

You should integrate network scanning into your broader security operations to create an automated, closed-loop system for vulnerability lifecycle management, like connecting your vulnerability scanner to SOAR and SIEM solutions.

This creates a powerful workflow. 

For example, when a scan discovers a critical vulnerability on a key server, it can trigger a real-time alert in the SIEM. The SIEM can then initiate a SOAR playbook that automatically opens a high-priority ticket in a system like Jira or ServiceNow, assigns it to the correct IT administrator and populates the ticket with all necessary remediation details. 

This automated process ensures you track vulnerabilities from discovery to resolution with clear metrics for compliance and significantly speeds up your response time.

A one-size-fits-all scanning policy is inefficient and can be dangerous. 

Customize your scan profiles based on different network segments' specific risks, technologies and operational requirements.

While you should always use lighter, less frequent scans for low-risk segments, pay special attention to these unique environments:

Cloud (AWS, Azure, GCP): Traditional network scanners have blind spots in the cloud. Augment your strategy with native tools. In these highly dynamic environments where assets constantly spin up and down, lightweight, agent-based scanning is often more effective than periodic network-based scans.

OT/industrial control systems (ICS): These environments require extreme caution. Never run a standard IT network scan on an OT network. Always start with a passive-only scanning approach to safely discover and identify assets without risk of disrupting critical industrial processes. If you need active scanning, use policies specifically designed and certified for OT environments.

Scanning generates vast amounts of data, which can be overwhelming without the right knowledge. Train your security and IT teams to read scan reports, understand vulnerability severity and prioritize remediation efforts.

Proper training prevents teams from wasting time chasing low-risk issues or misinterpreting scan results. Encourage collaboration between security, network and operations teams to improve communication and speed up fixing vulnerabilities.

Continuous education and skill development also help your team stay current with evolving threats, new scanning technologies and best practices.

Finally, take advantage of automation wherever possible. Automate scan scheduling, results analysis and vulnerability tracking.

Set up alerts for critical vulnerabilities, newly discovered assets or unusual scan findings so your team can respond quickly to emerging threats. Automation speeds up detection and remediation while reducing human error and operational overhead.

Many modern scanning and vulnerability management platforms offer built-in automation capabilities that seamlessly integrate with your existing security tools.

Following these network scanner best practices will improve visibility, reduce false positives, focus on real risks, and keep your network safe without disrupting business operations. These strategies create a solid foundation for proactive security that adapts as your network evolves.

Want to elevate your network scanning and vulnerability management? Discover how Tenable Vulnerability Management can help you automate scanning, prioritize risks and accelerate remediation.