Understanding external vulnerability scanning
External vulnerability scanning is a way to find weaknesses in your public-facing systems by testing them from outside your network. This means you see your environment the same way an attacker on the internet would see it.
In practice, a security vulnerability scanner sends safe probes to websites, APIs, VPNs, internet‑exposed gateways, and public IPs to see what is exposed and how it responds. The scanner tests from outside your network perimeter, just as an attacker would. It looks for outdated software, bad configurations, and other conditions that could be turned into real attacks.
The main goal is simple: find and fix gaps before someone else finds them for you. Because the scanner does not rely on internal access or credentials, it shows you how your perimeter actually looks from the open internet.
Perimeter security: How well your outer defenses protect internal systems.
Attack surface: All the ways an attacker could interact with your environment from the outside.
Public-facing assets: Any system or service that can be reached directly from the internet.
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External vs internal vulnerability scanning
External and internal vulnerability scanning answer different questions for you, and you need both views for a complete picture.
External scanning looks only at what the internet can reach. It tells you, "If I were an attacker on the outside, where could I start?" Internal scanning runs from inside your network and often uses credentials to log into systems and see much deeper details.
Key differences include:
Scope and perspective: External scans only see assets and services exposed to the internet, which shows your real external attack surface. Internal scans reach systems behind firewalls and inside private networks.
Authentication levels: External scans are usually unauthenticated, because attackers do not start with passwords. Internal scans often use accounts or keys so they can check installed software, patches, and local configuration.
Risk types identified: External scans focus on perimeter defenses and public-facing vulnerabilities, such as open admin interfaces. Internal scans pick up issues that enable lateral movement, privilege escalation, or insider abuse.
Compliance requirements: Some standards set explicit expectations—for example, PCI DSS requires quarterly external ASV scans—while others such as ISO 27001 and SOC 2 expect an effective vulnerability management process without prescribing specific scan frequencies. Both external and internal views are typically needed to demonstrate comprehensive coverage.
A simple way to think about it:
External scanning: "How do I look from the outside?"
Internal scanning: "How safe am I once someone is already inside?"
You should not choose one over the other. External-only scanning misses internal paths an attacker might use after the first breach, while internal-only scanning misses the front door issues that let them in at all.
Why external vulnerability scanning matters for modern organizations
As you move more services to the cloud and rely on SaaS and remote access, your external attack surface grows in ways that are hard to track by hand. External vulnerability scanning helps you keep up.
Attackers constantly scan the internet for easy targets. If you expose a vulnerable service or misconfigured firewall, it will usually be found quickly. Regular external scans give you a chance to catch and fix those issues before someone else takes advantage of them.
External scanning also supports governance and assurance. Many frameworks expect scheduled vulnerability assessments and timely remediation. PCI DSS, for example, mandates quarterly external scans by an Approved Scanning Vendor (ASV), with rescans required until all high-severity vulnerabilities are resolved. These reports are useful when you talk to auditors, customers, and cyber insurers.
It also helps you control shadow IT and drift. Development teams can create new cloud resources in minutes, sometimes outside standard processes. Old projects can stick around long after they were supposed to be shut down. External scanning is often the only realistic way to spot these unknown or forgotten internet-facing assets.
Digital footprint: Everything about your organization that is visible on the internet.
Attack surface management: The practice of finding, tracking, and reducing those external entry points over time.
PCI DSS external scanning requirements
Organizations that process credit card data must comply with PCI DSS, which mandates quarterly external vulnerability scans by an Approved Scanning Vendor (ASV). Key requirements include:
Quarterly scans: Run external scans at least every 90 days
Change-triggered scans: Scan after significant network changes that could affect cardholder data exposure
Passing scans: Achieve a passing scan with no vulnerabilities rated 4.0 or higher (CVSS)
Rescan requirement: Rescan after remediation until all high-severity issues are resolved
ASV certification: Only ASV-certified vendors can provide scans for PCI compliance
Note that ASV scans complement but don't replace penetration testing, which PCI DSS also requires annually and after significant changes.
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External vulnerability scanning in cloud environments
Cloud environments change the game for external vulnerability scanning. As more workloads and data move to cloud services, the external attack surface grows and changes quickly. Auto-scaling, containers, and short-lived build machines mean assets can appear and disappear within minutes. The old approach of scanning a fixed IP list from your data center does not work well anymore.
Cloud providers assign dynamic IP addresses to many resources, so the address in use today might be different tomorrow. Auto-scaling, containers, and short-lived build machines mean assets can appear and disappear quickly.
At the same time, cloud adds many new kinds of entry points:
Storage endpoints: Public buckets and file shares.
Managed databases: Services that can be opened to the internet by a simple checkbox.
API gateways and load balancers: Front doors to microservices and backends.
CI/CD and registries: Developer tools that sometimes expose admin interfaces.
Many of the highest‑risk problems here are misconfigurations, not just unpatched software. A database that is open to the world, even if fully patched, is still a major risk if internal data is behind it. Think publicly accessible storage buckets or overly permissive security groups.
Because of this, a cloud-ready security vulnerability scanner needs to blend traditional network checks with cloud-aware context. Specifically, it should:
Analyze effective exposure paths: Trace how traffic can reach a resource through load balancers, security groups, network ACLs, and routing tables—not just whether a port is open
Incorporate identity blast radius: Understand which IAM roles, service accounts, and cross-account permissions are attached to exposed resources, since a compromised service with admin rights is far more dangerous than one with read-only access
Track resource relationships: Map how exposed services connect to databases, storage, and other backend systems to understand lateral movement paths
Validate cloud-specific misconfigurations: Check for public S3 buckets, overly permissive security groups, exposed RDS instances, and publicly accessible Kubernetes API servers
Ephemeral resources like serverless functions and short-lived containers make it hard to catch everything with one-time scans. A better approach is to use cloud-native scanning that tracks resources as they come and go, and then focuses deeper external checks on anything that is actually reachable from the internet.
Best practices for implementing external vulnerability scanning
To get real value from external vulnerability scanning, you need a small set of habits, not just a tool. These habits keep your scans focused, repeatable, and useful to your teams.
Start by defining clear policies. Decide which systems must be scanned, how often, and how quickly different severities should be fixed. Make sure these expectations are written down and shared with owners.
Comprehensive asset inventory: Keep a live list of all external-facing assets, including cloud endpoints. Use several discovery methods such as DNS lookups, certificate analysis, and cloud API queries to avoid blind spots.
Risk‑based prioritization: Treat issues differently based on impact and exploitability. Augment CVSS scores with signals like public exposure, known exploitation status (for example, CISA KEV catalog), identity blast radius, and business criticality. Focus first on high-value systems, sensitive data, and vulnerabilities that combine into toxic chains.
Next, connect scanning to how you build and ship systems. Embedding external checks into your CI/CD pipelines helps you catch dangerous exposures before they go live. This "shift-left" move saves your teams from late surprises.
You should also aim for continuous or frequent scanning rather than rare, manual runs. Because infrastructure is dynamic, a one-time clean bill of health does not last long.
Finally, make sure each finding has a clear home. Map vulnerabilities to service owners or teams, set remediation SLAs, and track whether fixes actually work through follow-up scans.
Common external scanning pitfalls and how to avoid them
Watch out for these gaps that weaken external scanning programs:
Static IP lists only: Cloud resources use dynamic IPs that change constantly. Use cloud API discovery instead of maintaining manual IP lists.
Ignoring identity paths: A vulnerability matters more when the compromised service has admin rights or cross-account access. Correlate exposures with identity blast radius.
Missing ephemeral assets: Short-lived containers and serverless functions can expose vulnerabilities for hours before disappearing. Use continuous scanning, not weekly snapshots.
No ownership mapping: Findings without clear owners sit unresolved. Tag resources with team identifiers and route alerts automatically.
Pure CVSS triage: Severity scores don't account for exposure or business context. Prioritize based on exploitability, exposure, and data sensitivity.
Not scanning after changes: New deployments can introduce exposures. Integrate scanning into CI/CD pipelines and change management workflows.
Aggressive scan rates: Overly aggressive scanning can trigger rate limits or disrupt production. Use safe scanning modes with appropriate throttling.
Key metrics for external scanning programs
Track these KPIs to measure program maturity and demonstrate security improvement:
Mean time to validate (MTTV): How quickly you confirm whether a detected exposure is exploitable (target: under 24 hours for critical findings)
Mean time to remediate (MTTR): How long it takes to fix validated exposures (target: 7 days for critical, 30 days for high)
Exploitable exposure count: Number of internet-facing vulnerabilities that are both reachable and exploitable (goal: zero critical)
Coverage percentage: Proportion of internet-facing assets scanned in the last 7 days (target: 100%)
Ownership SLA adherence: Percentage of findings routed to correct teams within defined timeframes (target: 95%+)
Exposure trend: Month-over-month change in total exposed services and vulnerabilities
Shadow asset discovery rate: New internet-facing assets found that weren't in your inventory
How Wiz transforms external vulnerability scanning with cloud-native context
Wiz approaches external vulnerability scanning by combining what the internet can see with what your cloud environment actually looks like inside. This gives you both the outside view and the internal context you need to act fast.
Wiz ASM automatically discovers all of your internet-facing assets across cloud providers. It uses agentless cloud connections, so it finds exposed virtual machines, storage buckets, databases, Kubernetes ingress points, and APIs—even when they have dynamic IPs or were created outside official processes.
What makes Wiz different is how it connects external findings to internal cloud details using the Wiz Security Graph. When Wiz finds an exposed service with a vulnerability, it also shows:
Which identities have access and whether they are overprivileged.
How an attacker could move laterally from that service to other systems.
Whether sensitive data is reachable along that path.
This “toxic combination” view turns a flat list of CVEs into a ranked set of real attack paths. It helps you focus on the exposures that truly matter, not just the ones with the loudest severity score.
Wiz also traces many issues back to code and configuration. If an exposure comes from an infrastructure as code file, Wiz can point to the exact template and likely owner. That shortens the path from detection to fix and makes it easier to prevent the same issue from coming back.
Wiz UVM extends this by unifying vulnerability management across your entire cloud stack—from code to cloud to containers. It correlates external exposures with internal vulnerabilities, misconfigurations, and identity risks to show you which combinations create real attack paths. Instead of treating every CVE the same, Wiz UVM prioritizes based on exploitability, exposure, and blast radius, so your teams fix what actually matters first.
Because Wiz brings together CSPM, CWPP, CIEM, DSPM, and external scanning in one platform, you see all of your risks in one place instead of juggling separate tools. You get a single prioritized queue that already accounts for context, exposure, and business impact. Book a demo today!
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