Vulnerability Analysis

A vulnerability is a weakness in an information system, system security procedures, internal controls, or implementation that could be exploited or triggered by a threat source.

NIST Glossary – https://csrc.nist.gov/glossary/term/vulnerability

Vulnerability analysis includes the detection, assessment, classification and treatment based on the risk they pose to the company.

Vulnerability Identification

A security team can detect vulnerabilities following different approaches. As part of a vulnerability management process, it is good practice to subscribe to the mailing lists in which vulnerabilities and related countermeasures are disclosed. This service is usually offered by the vendor or, if not available, through third parties. It is a very time expensive but necessary task. You must perform it on a daily basis to promptly detect vulnerabilities and to comply with several standards/regulations.
Other inputs could derive from the analysis of the hardening procedures reports/tasks, the periodic review of the access rules and of the company policies and procedures.

Tools

Thanks to tools like Nessus and OpenVAS, it is possible to partially automate the discovery and analysis of vulnerabilities. After verifying the active hosts and the related services, we can deepen our analysis and determine the operating system and application versions.

As shown in the figure, Nessus provides the list of vulnerabilities to which each analyzed host is potentially vulnerable. Potentially because the scanner does not attempt to exploit the vulnerability. This phase, often manual, is not part of the vulnerability analysis process and is normally carried out within a penetration test.

CVSS

In the report, vulnerabilities are classified according to the CVSS (Common Vulnerability Scoring System), a framework used to classify software vulnerabilities. CVSS is an important tool that simplifies the vulnerability management process.

Let’s pretend you are in a meeting with the company management and you have to share the results of your vulnerability analysis. The test results were not good: you need at least three system administrators for one month to implement the remediation plan. You need to install patches, implement countermeasures, and you have to do it fast. During the meeting, you could try to tell management that you found several RCE-type vulnerabilities on systems deployed in your DMZ. Attackers do not need system/applications credentials to perform the attack and exploits are readily available on the Internet. Or you could report the presence of several CVSS 10 vulnerabilities on critical systems.
For more information on CVSS, in its two versions 2.0 and 3.0, I suggest reading our article.

CVE & NVD

Each vulnerability has a Common Vulnerability and Exposures (CVE) ID, in the form of CVE-YYYY-NNNN. The assignment of an ID to each vulnerability allows one to keep track of it and to automate/simplify the integration of the different tools available to an analyst.

Let’s say you have just detected a vulnerability on your firewall appliance. Since it is a well-known vulnerability, it has got a specific CVE-ID. Assuming that your firewall vendor catalogues their vulnerabilities and patches by CVE, it is going to be easy to ask the vendor for additional information, search for the relevant patches and to minimize the possible impacts of applying remediation on the infrastructure. Furthermore, it is going to be easy to find the relevant signature in your IDS/IPS.
CVE is operated by “The Mitre Corporation“. More details can be obtained on the cve.org website.

NVD (National Vulnerability Database) is managed by NIST (National Institute of Standards and Technology). NVD is a vulnerability database: for each CVE information such as countermeasure, criticality and impact is provided.

CWE & OWASP

CWE (Common Weakness Enumeration) is a list of common types of hardware and software defects that have security implications. The CWE list can be used as a framework to describe and communicate such vulnerabilities in terms of CWEs. The CWE Top 25 Most Dangerous Software Weakness List is a list of the most common programming errors that can lead to software vulnerabilities. Vulnerabilities present in the CWE Top 25 are usually easy to detect and exploit. For example, the CWE-79 is related to Cross-Site Scripting while the CWE-89 to SQL Injection. A similar project is Top Ten Owasp (Open Web Application Security Project). Compared to the CWE Top 25, the Top Ten OWASP focuses solely on vulnerabilities of web applications.
The CWE Most Important Hardware Weakness List serves the same purpose, but it focuses on hardware defects.

Vulnerabilty Analysis steps

Vulnerability analysis comprehends different phases.

Preparatory phase

it is not possible to carry out a thorough and reliable analysis without having a deep knowledge of the infrastructure/application under examination. If the procedure for managing IT services and their related assets is not implemented, it is not going to be possible to classify and prioritize vulnerabilities. Let’s say our vulnerability scanner found 300 vulnerabilities on approximately 30 hosts. Which vulnerabilities should I prioritize? Which one shall I remediate immediately? The answer relies not only on the vulnerability severity but also on how important are the hosts and services affected by it.

Discovery and analysis of vulnerabilities

You performed vulnerability scans, you analysed security advisories, system configurations, your company policies and procedures. You have a comprehensive list of vulnerabilities. You can now prioritise them, identify false positives (and false negatives), and improve the results with your knowledge of the infrastructure/application. At the end of this phase, your security team will produce a vulnerability scan report.

Post assessment

It is now possible to define a remediation plan. The remediation plan is not a mere list of the patches, countermeasures and IPS rules: if your analysis has shown the presence of several SQL Injection, CRSF and XSS vulnerabilities in the software developed internally (or by a specific supplier), you must immediately schedule secure programming training classes for your developers.

If these kinds of vulnerabilities are found on software purchased from third parties, you must tell the service owner to look for a new vendor.

While the first scenario is a symptom of a poor security awareness policy, the second one highlights a poor supplier policy: do you review your supplier security policies after you sign a contract? Do you ask to review their development procedures? Do they regularly perform code reviews? Is security fully integrated into their development life-cycle?
Outsourcing has hidden costs that you always need to consider.

Once the remediation plan has been implemented, the security team shall verify it has been properly implemented. Depending on its size, the implementation of the remediation activities can take several weeks, if not months. It is crucial to plan periodic meetings to keep the team focused and to check the progress.

What’s next?

In the next articles, we will analyse the vulnerability management process and its implications for regulations like ISO27001 and PCI-DSS. In the meantime, we suggest reading our articles about CVSS and the Metasploit lab.