Cyber Security, External Network Vulnerability Scans

External vs. Internal Vulnerability Scans: What’s the Difference?

September 15, 2025

In order to bolster security and keep a company secure from cyberattacks, enterprises must have vulnerability scans integrated into their cybersecurity assessments. These scans make up the foundation of these assessments to ensure that there are no open vulnerabilities in the infrastructure. Organizations face both internal and external risks, so maintaining network security needs to be proactive. External hackers probing public assets and insider threats are both part of the threat landscape. That’s why it’s so important to not only have external scans and internal scans in place but to know the difference between them and design a bolstered and secure defense strategy.

It’s essential to evaluate and identify system weaknesses, applications, and networks prior to coming up against an attack. That’s exactly what vulnerability scans do. These scans can also assist in broader cybersecurity assessments in order to give early warnings for potential risks. These scans can be both manual and automated. Automated scans use tools that systematically check systems, and manual scans involve cybersecurity professionals performing the assessment hands-on. Whether a business chooses to have automatic, manual, or both types of scans in place, both are paramount in identifying security flaws and mitigating them before an attack happens.

When a company runs a scan from outside its network perimeter, it’s called an external vulnerability scan. During this scan public public-facing assets like websites, firewalls, VPN’s,and DNS servers are evaluated. They scan as if looking inward and can find vulnerabilities that are easily exploited without gaining internal access. Common tools used for these types of scans include Qualys, Nessus, and OpenVAS. They identify open ports, unpatched software, and outdated SSL certificates. In addition, regulatory compliance, such as PCI DSS (Payment Card Industry Data Security Standard), requires external scans to be completed regularly for any company that handles credit card transactions.

Insider risks are often just as troublesome as outside threats, if not more. That’s why internal vulnerability scans are equally important. These scans focus on certain risks, including unpatched systems, privilege escalation opportunities, and misconfigurations. If these scans are not done regularly, their pathways are opened up for attackers to move laterally throughout the network. Internal scans use many of the same tools as external scans, but are configured differently and require access to file servers, IP ranges, and databases. They can find vulnerabilities that external scans are unable to see.

External and internal scans have some key differences that are important to mention. External scans are responsible for looking at the internet-exposed attack surface, while internal scans are responsible for the vulnerabilities that can be exploited internally or on the inside of the network. Perspective and access are also important to note. The external scans pick up vulnerabilities that the attacker can exploit without having credentials to access the system. Internal scans simulate an attacker who is already inside the network with credentials. These credentials can allow the attacker to gain deeper access through privilege escalation. Frequency is also notable. External scans should be run at least monthly, while internal scans may need to be run more frequently, depending on policy and changes that occur.

Since the two Vulnerability scans have different tasks, it’s important that they both have a role in protecting the security infrastructure of the company. If only one is used, there will be blind spots that an attacker can easily exploit. An external scan will find a misconfigured firewall, but not be able to spot an outdated database that is easily accessed from inside the network. Oftentimes, an attacker will gain access to internal systems through phishing and then be able to exploit internal vulnerabilities. If both internal and external scans are used, the attack surface will be protected by a layered security approach, which will mitigate vulnerabilities regardless of where they originate.

In order to have vulnerability scanning included in your security program and architecture, planning, and commitment are required. Both external and internal scans need to be scheduled regularly to maintain visibility of the threats. Using automated scans where feasible will ensure human resources are free for remediation and analysis. There should be a plan as to who is responsible for what tasks, and identify the security and IT operations teams. The plan must be reviewed, and the workflow prioritized based on risk. Lastly, tracking is key to maintaining robust protection. This will ensure that the scans are an effective defensive tool rather than just an exercise that checks a box.

Bottom line, both internal and external scans are important in securing a company’s cybersecurity infrastructure. It’s imperative to know the difference between the types of scans, leveraging them both in a way that is proactive and efficient, so they can be a valuable addition to the overall cybersecurity assessment. This requires the right team to implement scans, assess the results, and apply the remediations. Cyber Bark provides comprehensive automated vulnerability scans as well as expert personnel to assist in understanding the results so the cybersecurity infrastructure and network can be bolstered and secured for the long haul.