# Internal vs External Vulnerability Scans: What Each One Tells You

"We scanned your network" can mean two very different things. An external scan looks at the client from the internet, the way any stranger can. An internal scan looks from inside the office or the cloud network, the way an attacker would after getting a foothold. They find different problems, they answer different questions, and mixing them up in a report leads to bad decisions.

## External scans: the front door

An external scan runs from outside the client's network against their public IP addresses and hostnames: the firewall, VPN gateway, email server, websites and any cloud services they expose.

It answers: **what can anyone on the internet reach, and is any of it vulnerable?**

Typical findings:

- Remote access services (RDP, SSH, VPN portals) exposed to the internet
- Outdated firmware on firewalls and VPN appliances
- Weak TLS settings or expired certificates
- Admin interfaces that should never be public
- Forgotten test servers and old DNS records still pointing at live systems

External findings are usually few in number and high in consequence. Edge devices such as VPN appliances and firewalls show up on the CISA Known Exploited Vulnerabilities list again and again, because they are the easiest way in.

## Internal scans: everything behind it

An internal scan runs from a machine or agent inside the network and looks at workstations, servers, printers, switches and everything else that isn't public.

It answers: **if someone gets in, how far can they go?**

Typical findings:

- Missing operating system and application patches
- Outdated browsers, PDF readers and office software
- Old protocols still enabled (SMBv1, unsigned SMB, legacy TLS)
- Default credentials on printers, cameras and network gear
- End-of-life systems nobody has replaced

Internal scans produce far more findings, especially when they're credentialed. That is normal: there is much more to look at.

## Side by side

| | External | Internal |
|---|---|---|
| Runs from | The internet | Inside the network |
| Targets | Public IPs, hostnames, web apps | Workstations, servers, network devices |
| Main question | What can a stranger reach? | How far could an intruder get? |
| Finding volume | Low | High |
| Typical priority | Fix fast; often exposed and exploited | Fix by risk; prioritize known exploited issues |
| Common requirement | PCI DSS quarterly external scans (by an ASV) | PCI DSS quarterly internal scans, cyber insurance questionnaires |

## Why you usually need both

An external scan alone tells you the doors are locked but nothing about what's inside. Phishing, a stolen password or a compromised vendor gets an attacker past the edge without touching any of those doors, and then the internal findings decide how bad the day gets.

An internal scan alone misses the most exposed systems entirely, and those are the ones that get hit by automated attacks within days of a new vulnerability being announced.

A sensible baseline for most small and mid-sized clients is an external scan at least monthly and after any firewall or DNS change, and a credentialed internal scan monthly.

## Report them separately

The most common reporting mistake is merging both scans into one long list. Three critical internal findings on workstations and one critical finding on the VPN gateway are not the same kind of problem, and a merged table makes them look identical.

Better:

- **Separate sections** for external and internal results, each with its own scope statement (which IPs, which subnets, credentialed or not)
- **External first**, because those findings are reachable by anyone
- **A clear note when one is missing**: "This report covers the internal network only. No external scan was performed this month."

That last line is easy to skip and important to keep. A client who reads "no critical findings" on an internal-only report may reasonably assume their internet-facing systems were checked too.

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*Related: [How often to run vulnerability scans](https://varaxontech.com/guides/how-often-to-run-vulnerability-scans?utm_source=hashnode-blog&utm_medium=referral&utm_campaign=internal-vs-external&utm_content=inline) · [Vulnerability scan vs penetration test](https://varaxontech.com/guides/vulnerability-scan-vs-penetration-test?utm_source=hashnode-blog&utm_medium=referral&utm_campaign=internal-vs-external&utm_content=inline)*