Tag Archives: Nessus

Vulnerability Management for Network Perimeter

Network Perimeter is like a door to your organization. It is accessible to everyone and vulnerability exploitation does not require any human interactions, unlike, for example, phishing attacks. Potential attacker can automate most of his actions searching for an easy target. It’s important not to be such of target. 😉

Vulnerability Management for Network Perimeter

What does it mean to control the network perimeter? Well, practically this process consist of two main parts:

  • Assessing network hosts that are facing Internet using some Network Scanner (Nessus, OpenVAS, Qualys, MaxPatrol. F-Secure Radar, etc.)
  • Assessing application servers, e.g. Web Servers, on these hosts using some special tools, e.g. Web Application Scanners (Acunetix, Burp Suite, Qualys WAS, Tenable.io WAS, High-Tech Bridge ImmuniWeb, etc.)

Active scanning is a good method of perimeter assessment. Dynamics of the assets is relatively low, comparing with the Office Network. Perimeter hosts usually stays active all the time, including the time when you are going to scan scanning them. 😉

Most of the dangerous vulnerabilities can be detected without authorization: problems with encryption (OpenSSL Heartbleed, Poodle, etc.). RCE and DoS of web servers and frameworks (Apache Struts and Equifax case)

The best results can be achieved with scanners deployed outside of your network. Thus, you will see your Network Perimeter the same way a potential attacker sees it. But certainly, you will be in a better position:

  • You can ask your IT administrators to add your network and WAS scanners in white list, so they will not be banned.
  • You can check and correlate scan results of remote scanner with (authenticated?) scan results produced by the scanner deployed in your organization’s network and thus filtering false positives.

What about the targets for scanning? How should you get them?

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Study Vulnerability Assessment in Tenable University for free

Not so long ago, Tenable presented renewed online training platform – Tenable University. It is publicly available even for non-customers, for example, for Nessus Home users. However, not all courses are available in this case.

Login screen

I decided to check it out, registering as non-customer.

Sign up

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Exploitability attributes of Nessus plugins: good, bad and Vulners

Exploitability is one of the most important criteria for prioritizing vulnerabilities. Let’s see how good is the exploit-related data of Tenable Nessus NASL plugins and whether we can do it better.

Nessus exploitability

What are the attributes related to exploits? To understand this, I parsed all nasl plugins and got the following results.

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Scaner-VS: Vulnerability Management solution for Russian Military

Scaner-VS is a Vulnerability Assessment system developed by Moscow-based NPO Echelon. It’s pretty popular in Russian government organizations, especially in Russian Army, because it comply all government requirements, has all necessary certificates and is relatively cheap.

Scaner-VS webgui

As for requirements and certificates, NPO Echelon itself is an important certification authority, so they know how to do the things right. It’s not a secret product or something. You can request trial version freely at http://scaner-vs.ru/version-for-testing/. But note, that it is only available in Russian. I am also sorry, but screenshots in this post will be also in Russian. I will try to do my best to describe them properly.

When you fill the form on Echelon website, you will soon get a link to 3.3 gb .iso file by email. Run it in VirtualBox virtual machine (choose Debian 64 or Debian 32).

Here is a boot menu. Choose first default option.

Scaner-VS boot

Some seconds later you will see Linux desktop environment with Scaner-VS web-GUI opened in Firefox.

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Problems of Vulnerability Prioritization and Detection

It’s the third part of our talk with Daniil Svetlov at his radio show “Safe Environment” recorded 29.03.2017. In this part we talk about Vulnerability Prioritization and Detection:

  • Common Vulnerability Scoring System (CVSS)
  • Environmental factor
  • Manual and  automated vulnerability detection
  • Unauthenticated and authenticated  scanning
  • Why vulnerability scanners are so expensive and why the can’t detect everything

Scanner does not detect all vulnerabilities

Video with manually transcribed Russian/English subtitles:


– Here also the question how to prioritize vulnerabilities properly. Because if you have, as you said, two Linux servers and 20 workstations running Windows, then in principle, you may not need to do prioritization. But if you have fifteen hundred servers: some of them are on perimeter, some are in your DMZ, some are in the internal network. It is still necessary, probably, to understand correctly which vulnerabilities and where should be patched in in the first place.

Yes, this is absolutely true and it’s a very good question. How to prioritize?

Common Vulnerability Scoring System

A natural way. If we look at vulnerabilities with a CVE identifier, for them in the US National Vulnerability Database we can find CVSS Base Score. It is an assessment of vulnerability criticality level.

How is it calculated?

Some person fills the questionnaire: can it be remotely exploited – no, is there public exploit – no, etc.

CVSS framework

The result is a CVSS vector – this is a line in which you can see the main characteristics of this vulnerability and CVSS Base score is the score from 0 to 10 depending on criticality.

This is a natural way of prioritization. But sometimes this method does not give very good results.

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