Vulnerability Scanning Explained: What It Is, How It Works, & Why It Matters
Jenny Goldschmidt
Consumer Sales Lead at Red Sentry
Anna Fitzgerald
Senior Content Marketing Manager
This article is written and contributed by Red Sentry, a proud Secureframe partner.
As organizations manage a growing attack surface, vulnerability scanning provides a repeatable way to find known security weaknesses before attackers can exploit them. It is a foundational security practice and an important part of many compliance and vulnerability management programs.
But a scan is not the same as a penetration test, and finding vulnerabilities is not the same as managing them. This guide explains what vulnerability scanning is, how it works, which types of scans organizations use, and how to turn scan results into meaningful risk reduction.
What is a vulnerability scan?
A vulnerability scan is an automated examination of systems, networks, applications, or cloud environments for known security weaknesses. Vulnerability scanning is the recurring security practice of running these scans, reviewing the findings, and verifying that identified issues are addressed. A vulnerability scanner gathers information about assets such as software versions, open ports, services, and configurations and compares it with vulnerability databases, security advisories, and configuration rules.
Scanners can identify issues such as:
- Outdated or unsupported software
- Missing security patches
- Known Common Vulnerabilities and Exposures (CVEs)
- Insecure configurations
- Exposed ports and services
- Weak encryption or authentication settings
- Web application weaknesses such as cross-site scripting or SQL injection
The scanner then produces findings that usually include affected assets, severity ratings, supporting evidence, and suggested remediation. Security teams validate and prioritize those findings based on exploitability, asset importance, exposure, and business impact.
Vulnerability scanning is valuable because environments change constantly. New vulnerabilities are disclosed, systems are deployed, configurations drift, and applications gain new dependencies. Regular scanning helps organizations detect these changes and reduce the time that weaknesses remain exposed.
How does vulnerability scanning work?
Vulnerability scanning works by using specialized software to systematically scan and analyze the operating systems and major software applications running on the host devices on a network. The software searches for outdated software versions, missing patches, misconfigurations, and other security weaknesses and matches them with with information on known vulnerabilities stored in the scanners’ vulnerability databases.
It then generates a detailed report highlighting the identified vulnerabilities and their severity levels.
Organizations can use this information to prioritize and address the vulnerabilities, applying patches, configuration changes, or other security measures to strengthen their defenses and reduce security risks.
A vulnerability scanning program generally follows six steps:
1. Define scope
Identify the assets and environments that the scan should cover. Scope may include public IP addresses, internal networks, endpoints, servers, web applications, APIs, cloud workloads, containers, and code dependencies. An accurate asset inventory helps prevent blind spots.
2. Configure the scan
Choose the appropriate scan type and configure credentials, policies, exclusions, and schedules. Teams should account for operational constraints because aggressive scans can affect fragile or production systems.
3. Discover assets and services
The scanner identifies active hosts, operating systems, open ports, installed software, running services, and other characteristics of the target environment.
4. Compare findings with known weaknesses
The scanner compares the collected information with sources such as CVE records, vendor security advisories, configuration benchmarks, and its own vulnerability intelligence. Some scanners also perform safe checks to confirm whether a weakness is present.
5. Analyze and prioritize results
The scanner generates a report, often using the Common Vulnerability Scoring System (CVSS) as one input. Teams should not prioritize by severity alone. A high-quality triage process also considers whether an asset is internet-facing, whether exploitation is known or likely, whether sensitive data is involved, and how important the system is to the business.
6. Remediate, verify, and repeat
Teams patch software, change configurations, remove unnecessary services, add compensating controls, or formally accept risk. A follow-up scan verifies that remediation worked. Because environments and threats change, vulnerability scanning should be repeated on a risk-based schedule and after significant changes.
Vulnerability scanning vs penetration testing
Vulnerability scanning and penetration testing are both forms of security testing designed to assess an organization’s security posture, but there are key differences.Â
A vulnerability scan is a high-level test that focuses on the identification, prioritization, and reporting of vulnerabilities using automated tools, whereas a pen test is a more in-depth test designed to not only discover but exploit vulnerabilities and potentially move deeper through your environment to discover additional threats.Â
A pen test can do this by using threat intelligence and modeling simulations to map out the application’s entire attack surface to identify possible attack entry points. Automated vulnerability scans, on the other hand, don’t necessarily consider the organization’s application business logic, which could lead to overlooked vulnerabilities or false positives.
That’s why a vulnerability scan is often just one part of the penetration testing process.Â
| Vulnerability scanning | Penetration testing | |
|---|---|---|
| Primary goal | Find known vulnerabilities at scale | Determine whether weaknesses can be exploited and what impact an attacker could achieve |
| Approach | Primarily automated | Expert-led, with automated tools supporting manual testing |
| Coverage | Broad and repeatable | Deeper testing of a defined scope |
| Frequency | Regular or continuous | Periodic and after major changes, based on risk or requirements |
| Output | A list of findings to validate and prioritize | Evidence of exploitable paths, business impact, and remediation guidance |
A vulnerability scan can cover many assets quickly, but it may return false positives and usually can't understand application business logic. A penetration test uses human judgment to explore attack paths and validate real-world impact. Many mature security programs use both: scans for recurring visibility and penetration tests for deeper assurance.
Recommended reading
Vulnerability Scanning vs Penetration Testing: Which Security Assessment Do You Need?
Vulnerability scanning vs vulnerability management
Vulnerability scanning is one activity within a broader vulnerability management program.
Scanning finds potential weaknesses. Vulnerability management governs what happens before and after the scan: maintaining an asset inventory, assigning ownership, assessing risk, setting remediation timelines, tracking exceptions, verifying fixes, and reporting on program performance.
An organization can run frequent scans and still have a weak vulnerability management program if findings aren't validated, prioritized, and remediated. The value comes from closing the loop between detection and risk reduction.
Recommended reading
A Step-by-Step Guide to the Vulnerability Management Process [+ Policy Template]
Types of vulnerability scans
Organizations often combine several scan types to cover different parts of their environment.
Internal and external network scans
External scans assess internet-facing assets such as public servers, firewalls, and gateways from an outsider’s perspective. Internal scans examine systems behind the perimeter and can reveal weaknesses that an attacker or malicious insider could exploit after gaining access.
Credentialed and non-credentialed scans
Credentialed scans use authorized accounts to inspect installed software, patch levels, local configurations, and other details that are not visible remotely. Non-credentialed scans test what can be observed without logging in. Credentialed scans generally provide greater depth, while non-credentialed scans help show an unauthenticated attacker’s view.
Web application and API scans
Dynamic application security testing examines running web applications and APIs for vulnerabilities such as injection flaws, cross-site scripting, insecure headers, and authentication weaknesses. Automated scanning should be complemented by secure development practices and, where warranted, manual testing.
Host and endpoint scans
Host-based scans inspect individual servers, workstations, and other devices for missing patches, vulnerable software, and unsafe configurations.
Cloud and container scans
Cloud scanning can identify vulnerable workloads, exposed services, insecure configurations, and risky identities or permissions. Container scanning examines images and running containers for vulnerable packages, secrets, and configuration issues.
Dependency and code scans
Software composition analysis identifies known vulnerabilities in open-source packages and dependencies. Static application security testing examines source code for patterns that may create vulnerabilities. These tools address related parts of application security and often feed the same vulnerability management workflow.
Compliance scans
Compliance-oriented scans evaluate systems against defined technical requirements or configuration benchmarks. For example, organizations that store, process, or transmit payment card data may need internal vulnerability scans and external scans performed by an Approved Scanning Vendor under PCI DSS, depending on scope and applicable requirements.
Benefits of vulnerability scanning
Conducting vulnerability scanning regularly can help maintain a proactive security stance, ensuring that new vulnerabilities are promptly detected and mitigated to safeguard critical data and assets.
Find weaknesses earlier
Regular scans can uncover known vulnerabilities and configuration problems before they are exploited. Earlier discovery gives teams more time to remediate issues and reduces exposure.
Prioritize security work
Scan data helps teams see which assets and weaknesses require attention. When findings are enriched with threat intelligence and business context, organizations can focus resources on risks that matter most.
Monitor a changing attack surface
New assets, software releases, configuration changes, and newly disclosed vulnerabilities can alter risk quickly. Recurring or continuous scanning provides visibility between point-in-time assessments.
Support audits and compliance
Scan reports, remediation records, exceptions, and re-scan results can provide evidence that security controls operate over time. The exact obligation depends on the framework, contract, risk assessment, and system scope. PCI DSS contains explicit vulnerability scanning requirements; other programs, including SOC 2 and ISO 27001, may make scanning an appropriate control without prescribing a universal quarterly schedule.
Measure program performance
Over time, teams can use scan data to track trends such as open findings by severity, time to remediate, recurrence, overdue vulnerabilities, and coverage of in-scope assets.
Limitations of vulnerability scanning
Vulnerability scanning is essential, but a clean scan does not prove that an environment is secure. Scanners can produce false positives by flagging weaknesses that are not exploitable in a specific environment. They can also produce false negatives when they cannot detect an unknown vulnerability, a flaw in application business logic, or a weakness that is not visible through the scanning method being used.
The results are only as complete as the scan’s coverage. Unknown or unmanaged assets may never be assessed, leaving security teams with blind spots. Even when a scanner identifies a genuine vulnerability, its severity score does not necessarily reflect the organization’s actual risk. Teams must also consider factors such as whether the affected asset is internet-facing, what data it handles, how important it is to business operations, and whether compensating controls are in place.
A vulnerability scan also captures conditions at a particular point in time. New vulnerabilities, system changes, and configuration drift can make a clean result outdated quickly. Organizations should therefore support vulnerability scanning with human review, accurate asset data, secure configuration and patch management, penetration testing, and continuous monitoring. Together, these practices provide a more complete picture of security risk than scanning alone.
Recommended reading
7 Benefits of Continuous Monitoring & How Automation Can Maximize Impact
How often should you run a vulnerability scan?
There is no single schedule that fits every organization. Scan frequency should reflect risk, rate of change, contractual commitments, and applicable requirements.
Many organizations scan critical or internet-facing assets continuously or frequently, scan the wider environment on a regular schedule, and run additional scans after significant changes or newly disclosed high-risk vulnerabilities.
PCI DSS specifies scanning frequencies for relevant cardholder data environments, including at least once every three months for certain internal and external scans. Other cybersecurity frameworks may expect organizations to define and follow a risk-based cadence.
How to choose a vulnerability scanning tool
Vulnerability scanning tools are automated tools that scan web applications and networks to look for and report vulnerabilities such as cross-site scripting, SQL injection, command injection, path traversal and insecure server configuration.
Here are some possible criteria to use when evaluating vulnerability scanning tools:
- Coverage for networks, endpoints, cloud infrastructure, applications, containers, and dependencies
- Support for credentialed and non-credentialed scanning
- Frequency and quality of vulnerability intelligence updates
- Accuracy and false-positive management
- Risk-based prioritization and actionable remediation guidance
- Integrations with asset inventories, ticketing systems, and compliance platforms
- Reporting, evidence retention, and role-based access controls
- Scalability, deployment model, and operational impact
The best tool is one that covers your organization’s actual attack surface and fits a repeatable remediation process, not simply the tool that generates the most findings.
Vulnerability scanning best practices
A scanner produces better results when it is part of a defined and repeatable program. Use these practices to improve coverage, accuracy, and remediation:
Maintain an accurate asset inventory. Include cloud resources, endpoints, applications, APIs, containers, and internet-facing assets so new or unmanaged systems do not escape scanning.
Combine scan types. Use internal and external perspectives plus credentialed scans where appropriate. One scan type rarely provides complete visibility.
Scan on a risk-based schedule. Scan critical and fast-changing systems more often, and trigger additional scans after significant changes or urgent vulnerability disclosures.
Protect credentials and production systems. Give scanning accounts only the access needed, store credentials securely, and test scan policies before running aggressive checks in production.
Prioritize with context. Consider exploitation activity, exposure, asset criticality, and compensating controls in addition to CVSS severity.
Define remediation ownership and timelines. Route findings to accountable teams and track them through resolution, exception, or formal risk acceptance.
Validate findings and re-scan. Investigate likely false positives and verify fixes with a follow-up scan.
Measure coverage and outcomes. Track whether in-scope assets are scanned as well as how quickly high-risk findings are remediated. A falling finding count is not meaningful if scan coverage is incomplete.
Using a vulnerability scanner with compliance automation
Vulnerability scanners identify weaknesses, while compliance automation platforms help connect those findings to controls, owners, evidence, and remediation workflows.
Secureframe can ingest vulnerability data from supported sources so teams can review findings alongside the rest of their compliance program. This helps centralize visibility, assign remediation work, monitor status, and retain evidence for audits. Organizations should still validate findings and make risk decisions based on their environment; automation improves the workflow but does not replace security expertise.
FAQs
What is a vulnerability scanner?
A vulnerability scanner is a tool that automatically scans systems, networks, or applications to identify known security weaknesses. These scanners compare your assets against databases of known vulnerabilities, such as CVEs (Common Vulnerabilities and Exposures), and flag any matches that could be exploited by attackers.
What is an example of vulnerability scanning?
A credentialed scanner might identify that an internet-facing server runs a software version affected by a known CVE. The security team validates the finding, patches or upgrades the software, and re-scans the server to confirm the vulnerability is no longer detected.
Is vulnerability scanning required for SOC 2?
SOC 2 does not impose one universal scanning frequency on every organization. Vulnerability scanning is commonly used as part of the controls that address risk identification, system operations, and change management. The appropriate scope and cadence depend on the organization’s risks, control design, and auditor expectations.
Is vulnerability scanning required for PCI DSS?
PCI DSS includes explicit internal and external vulnerability scanning requirements for in-scope environments. Applicable external scans must be performed by a PCI Security Standards Council Approved Scanning Vendor, and organizations should confirm the current requirements for their PCI DSS scope.
Can vulnerability scanning replace penetration testing?
No. Automated scanning provides broad, repeatable detection of known issues. Penetration testing applies human expertise to validate weaknesses, explore attack paths, and assess impact. The two practices complement each other.
Jenny Goldschmidt
Consumer Sales Lead at Red Sentry
Jenny Goldschmidt is a Senior Account Executive at Red Sentry, a cybersecurity company specializing in continuous penetration testing and vulnerability management. With years of experience helping organizations strengthen their security posture, Jenny works closely with IT leaders, auditors, and service providers to automate pentesting and make proactive vulnerability detection a standard—not a scramble. She’s passionate about helping companies move from reactive to continuous security, ensuring compliance with frameworks like SOC 2, PCI DSS, ISO 27001, and CMMC while reducing the time and cost of traditional assessments.
Anna Fitzgerald
Senior Content Marketing Manager
Anna Fitzgerald is a digital and product marketing professional with nearly a decade of experience delivering high-quality content across highly regulated and technical industries, including healthcare, web development, and cybersecurity compliance. At Secureframe, she specializes in translating complex regulatory frameworks—such as CMMC, FedRAMP, NIST, and SOC 2—into practical resources that help organizations of all sizes and maturity levels meet evolving compliance requirements and improve their overall risk management strategy.