Internal vs External Vulnerability Scans: Understanding the Difference

When it comes to establishing a robust mobile application security posture, vulnerability scanning is certainly the go-to option. But given the complex cybersecurity challenges of modern times, it might be complicated and challenging to implement vulnerability scanning properly.

According to the 2020 Edgescan Vulnerability Statistics Report, around 35% of the vulnerabilities discovered in external-facing apps were of critical or high risk. Given such levels of security risk, organizations must roll up their sleeves and turn to mature security practices like vulnerability scans to mitigate the underlying security risks and strengthen their security infrastructure.

Whether your organization is looking towards improving your already mature security posture or striving to enhance the security of your applications, this is a must-read blog post for you.

What is Vulnerability Scanning?

Vulnerability scanning is an automated process of proactively assessing applications, networks, and other security infrastructure for vulnerabilities. The process is usually performed by third-party security service providers or the IT department of the organization itself. Vulnerability scans are sometimes also performed by security attackers who are keen on finding points of entry into an existing network.

The vulnerability scanning process consists of classifying and detecting system vulnerabilities in communications equipment, networks, as well as computers. Apart from identifying security loopholes, the process of vulnerability scanning also keeps a check on the countermeasures that are necessary for effectively preventing possible attacks.

Now let’s talk about internal and external vulnerability scans and how important they are for your security infrastructure.

What is Internal Vulnerability Scanning?

Internal Vulnerability Scanning is the process of performing a scan from a location that already has access to the internal network of the system. These scans are mostly performed within the internal network environment. Contrary to the external scans, the internal vulnerability scans can see through the existing network for security vulnerabilities with a greater depth.

Internal scans have a number of unique benefits. Taking a proactive approach towards performing internal vulnerability scans helps in protecting the existing network from several known and unknown vulnerabilities. These types of scans work best when you need to verify that your patches have been implemented properly, or when you need to provide a detailed report regarding the existing vulnerabilities in the network for an in-depth analysis.

1. Credential vs Non-Credentialed Vulnerability Scans

When performing internal vulnerability scans, you get two major options to choose from - credential and non-credentialed scans. Each of them plays an essential role in identifying the depth and level of risk the vulnerabilities pose.

The purpose of credential scans is to utilize admin accounts and perform detailed checks by focussing on vulnerabilities that can’t be seen from within the existing network.  Non-credentialed scans, on the other hand, provide a brief view of the vulnerabilities by utilizing the existing networks that are hosted by the network host.

Although credential scans provide a deeper understanding of the existing vulnerabilities to an outsider (one who might attempt to exploit the known vulnerabilities via a phishing attempt or a malicious download), it is also important to understand that not all attacks come from the outside.

Some attacks may come from within the firewall as well. Since technology is becoming readily available and viable to use for non-technical users, the risk posed by an inside attack becomes more vivid and real. The non-credentialed scans help prevent those insider attacks by simulating what type of information a privileged insider has access to regarding the security posture of the organization. 

It might not sound that useful at first, but a non-credentialed scan should never be missed. It might be surprising for you to find out how much a regular insider can learn about your internal network infrastructure and with that information, they can do all sorts of damage. 

What is External Vulnerability Scanning?

External vulnerability scanning or perimeter scanning is performed from outside of the existing network. These scans are helpful in identifying vulnerabilities that threaten assets exposed to the outside world, i.e. the internet. External vulnerability scans are targeted at external IP addresses of your existing network.

The kind of information that you will find useful from these scans is not only the potential vulnerabilities but also a list of ports that are exposed openly to the internet. External scans work best when you need to identify the strength of your externally facing services.

Must Read: Difference between Agent-based and Network-based Internal Vulnerability Scanning

Why are Internal and External Vulnerability Scans Important for your Organization?

Internal and External Vulnerability Scans


Systems facing the internet are constantly being scanned for loopholes and attacked on a regular basis. Even if you are not running those scans, someone else would and you never know what intentions they have in their minds. Attackers are always scanning unpatched systems to exploit vulnerabilities and the global nature of the internet makes it even easier for them to carry on these attacks with utmost impunity.

Even if security patches exist within your system, attackers can utilize the lag time between the identification of the vulnerability and the implementation of an associated security patch. That is why it becomes essential to run vulnerability scans that help reveal the missing patches which need to be implemented on time. 

The threat of hackers and malware isn’t present only outside of your firewall, they can be present inside as well. The basic idea of threats originating from the internet is understood by many and makes sense to a lot of people, but what stays overlooked is the fact that these threats may originate from within the internal network as well.

These types of threats may include a number of disgruntled employees who have been keen on targeting systems from the inside, or malware (such as viruses or Trojans) which are downloaded via the Internet or a USB stick on a networked computer. When the malware enters the internal network, it looks out to target other systems and services on the internal network as well.

This is why both internal and external vulnerability scans are required in order to identify significant vulnerabilities. While an external scan detects vulnerabilities outside the firewall, the purpose of internal scans is to detect vulnerabilities within the firewall. Running an internal scan enhances the security of your internal network and prevents threat actors who have established a foothold inside your network from gaining more privileges.

Identifying and Mitigating Risks After Conducting Vulnerability Scans

The major aim of vulnerability scans is to provide you with a feedback loop that can help enhance the overall security posture of your organization. It is important to review the applied patches after each scan and get the remediation efforts approved by the IT and security teams.

It is important to act quickly after completing the vulnerability scans. Often at times, these scans are followed up with little or no analysis on what the next steps should be. A proper risk assessment must be performed in such a way that it makes sense to the organization apart from minimizing the existing possibility of overlooking potential threats.

For all the stakeholders within an organization, a specific tool called the vulnerability assessment risk matrix plays an important role in visually representing the scan results in an easily understandable format. The matrix may assist finance personnel, IT staff, security teams, operation stakeholders, along with the executive leadership of the organization in security-specific decision making.

Here’s a screenshot of the vulnerabilities detected in a test app and prioritized based on the CVSS score on a scale that ranges from 1- 10, with 10 being the highest severity and 1 being the lowest severity.





Although the number of medium and high vulnerabilities may be higher, you should focus on reviewing the less critical and rare vulnerabilities as well.

Final Thoughts

When it comes to assessing your organization’s stance on security, vulnerability scans are the primary source of knowledge. These scans provide instant support while rebuilding and strengthening the security posture of your existing network. If you want to bolster your security defences inside out, vulnerability scanning is surely the go-to process. Analysis and vulnerability scanning can go a long way in helping your organization fine-tune further security efforts, apart from providing you with one of the most decent returns on your security testing investment.

Published on Jul 5, 2021
Harshit Agarwal
Written by Harshit Agarwal
Harshit Agarwal is the co-founder and CEO of Appknox, a mobile security suite that helps enterprises automate mobile security. Over the last decade, Harshit has worked with 500+ businesses ranging from top financial institutions to Fortune 100 companies, helping them enhance their security measures.
Beyond the tech world, Harshit loves adventure. When he's not busy making sure the digital realm is safe, he's out trekking and exploring new destinations.


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