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Vulnerability Assessment and Penetration Testing

Vulnerability Assessment ( VA) and Penetrating Testing ( PT or PenTest ) are the most common types of technical security risk assessments or technical audits conducted using different tools. These tools provide best outcomes if they are used optimally. An improper configuration may lead to multiple false positives that may or may not reflect true vulnerabilities. Vulnerability assessment tools are widely used by all, from small organizations to large enterprises, to assess their security status. This helps them with making timely decisions to protect themselves from these vulnerabilities. Vulnerability Assessments and PenTests using Nessus. Nessus is a widely recognized tool for such purposes. This section introduces you to basic terminology with reference to these two types of assessments.

Vulnerability in terms of IT systems can be defined as potential weaknesses in system/infrastructure that, if exploited, can result in the realization of an attack on the system.

An example of a vulnerability is a weak, dictionary-word password in a system that can be exploited by a brute force attack (dictionary attack) attempting to guess the password. This may result in the password being compromised and an unauthorized person gaining access to the system.

Vulnerability Assessment is a phase-wise approach to identifying the vulnerabilities existing in an infrastructure. This can be done using automated scanning tools such as Nessus, which uses its set of plugins corresponding to different types of known security loopholes in infrastructure, or a manual checklist-based approach that uses best practices and published vulnerabilities on well-known vulnerability tracking sites. The manual approach is not as comprehensive as a tool-based approach and will be more time-consuming. The kind of checks that are performed by a vulnerability assessment tool can also be done manually, but this will take a lot more time than an automated tool.

Penetration Testing has an additional step for vulnerability assessment, exploiting the vulnerabilities. Penetration Testing is an intrusive test, where the personnel doing the penetration test will first do a vulnerability assessment to identify the vulnerabilities, and as a next step, will try to penetrate the system by exploiting the identified vulnerabilities.

Need for Vulnerability Assessment

It is very important for you to understand why Vulnerability Assessment or Penetration Testing is required. Though there are multiple direct or indirect benefits for conducting a vulnerability assessment or a PenTest, a few of them have been recorded here for your understanding.

Risk prevention

Vulnerability Assessment uncovers the loopholes/gaps/vulnerabilities in the system. By running these scans on a periodic basis, an organization can identify known vulnerabilities in the IT infrastructure in time. Vulnerability Assessment reduces the likelihood of noncompliance to the different compliance and regulatory requirements since you know your vulnerabilities already. Awareness of such vulnerabilities in time can help an organization to fi x them and mitigate the risks involved in advance before they get exploited. The risks of getting a vulnerability exploited include:

  • Financial loss due to vulnerability exploits
  • Organization reputation
  • Data theft
  • Confidentiality compromise
  • Integrity compromise
  • Availability compromise

Compliance requirements

The well-known information security standards (for example, ISO 27001, PCI DSS, and PA DSS) have control requirements that mandate that a Vulnerability Assessment must be performed.

A few countries have specific regulatory requirements for conducting Vulnerability Assessments in some specific industry sectors such as banking and telecom.

The life cycles of Vulnerability Assessment and Penetration Testing

This section describes the key phases in the life cycles of VA and PenTest. These life cycles are almost identical; Penetration Testing involves the additional step of exploiting the identified vulnerabilities.

It is recommended that you perform testing based on the requirements and business objectives of testing in an organization, be it Vulnerability Assessment or Penetration Testing. The following stages are involved in this life cycle:

  1. Scoping
  2. Information gathering
  3. Vulnerability scanning
  4. False positive analysis
  5. Vulnerability exploitation (Penetration Testing)
  6. Report generation

The following figure illustrates the different sequential stages recommended to follow for a Vulnerability Assessment or Penetration Testing:


In this article, we covered an introduction to Vulnerability Assessment and Penetration Testing, along with an introduction to Nessus as a tool and steps on installing and setting up Nessus.

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