Tag Archives: Linux

Dealing with Nessus logs

Debugging Nessus scans is a very interesting topic. And it is not very well described even in Tenable University course. It become especially interesting when you see strange network errors in the scan results. Let’s see how we can troubleshoot Nessus scans without sending Nessus DB files to Tenable  (which is, of course, the default way 😉 ).

Nessus Logs

Default logging

Let’s see default Nessus logs. I cleared log nessusd.messages file to have only logs of the latest scan:

# echo "" > /opt/nessus/var/nessus/logs/nessusd.messages

and restarted Nessus:

# /bin/systemctl start nessusd.service

I scan only one host (test-linux-host01, 192.168.56.12) with the Advanced scan profile. No default settings was set.

As you can see from the cpe report, it’s typical Linux host with ssh server:

typical Linux host with ssh

What’s in the logs?

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Microsoft security solutions against ransomware and APT

Last Tuesday I was invited to Microsoft business breakfast “Effective protection against targeted and multilevel attacks”. Here I would like to share some of my thoughts on this. Need to mention that the food was delicious and the restaurant of Russian Geographical Society is a very lovely place. 😉 Thanks, Microsoft!

Microsoft as a security vendor? O RLY?

Microsoft products are not actually my topic. To tell you the truth, personally I’d better live in a world without this massive Windows hegemony in desktop operating systems. I use Linux mostly. And even when I have to work in a Windows environment, it’s much easier for me to do all the work in some Linux virtual machine.

But in the real life almost every office network is build on Microsoft solutions. And if you are doing Vulnerability Management in any organization, you should deal with them too. The good news is that many security features are available out of the box in the MS products that you have already purchased. It’s just important to know about these features and use them right.

One more thing, why it’s interesting to learn more about Microsoft information security products. Microsoft developers, obviously, have direct access to Windows source code and know better how their own OS works. Many things are much easier for them to implement than for other security vendors. So, good chances that you will see in Microsoft products some interesting features, that other vendors don’t have (yet).

Drowning in data

The event began with an opening speech by Andrey Ivanov from Microsoft Russia.

Andrey Ivanov, "Effective protection against targeted and multilevel attacks"

I liked his thesis that “we are drowning in security data”:

  • Threat Intelligence from different sources that need to be implemented in your infrastructure and somehow validated. A good place to mention Vulners.com vulnerability feeds 😉
  • Threat Detection using logs, scanners, various protection tools, etc.
  • The overall number of SIEM inputs is growing faster than our resources. New IT system = new problems of SIEM configuration.

So, it would be nice if somebody, for example OS vendor, will provide all this as a service, right? 😉

Detect the undetectable

Then there was the keynote by Zbigniew Kukowski – one of the leading Microsoft information security experts.

Zbigniew Kukowski, "Effective protection against targeted and multilevel attacks"

Why is it necessary?

Here is what I would like to note from his report. First of all, great arguments why it is necessary. Ok, this is marketing. But the ability to explain (to sell) necessity of information security is important skill for any information security specialist now. It does not matter if you are working in a  security vendor, integrator or customer.

Zbigniew mentioned an interesting case: some Polish company, that lost $ 4.3 million in recent the Petya attack in 4 days. The cost of Information Security measures will be much less than the potential losses of business.

Another argument – attacks are not the entertainment for some individuals any more. Now it’s a well-organized criminal business. Dozens of people are working on popular malware tools, like Petya. That’s why ransomware tools are so popular now – cyber-criminals just want to return their development costs.

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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:

Prioritization

– 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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PHDays VII: To Vulnerability Database and beyond

Last Tuesday and Wednesday, May 23-24, I attended PHDays VII conference in Moscow. I was talking there about vulnerability databases and the evolution process of vulnerability assessment tools, as far as I understand it.

To Vulnerability Database and beyond

But first of all, a few words about the conference itself. I can tell that since the last year the event got even better. I’ve seen lot of new faces. Some people I didn’t know, but they knew me by my blog and accounts in social networks. What a strange, strange time we live in! I was very pleased to see and to talk with you all, guys! 🙂

PHDays is one of the few events that truly brings all Russian community of security professionals together. I’ve seen people I have studied with in university, colleagues from the all places where I have been worked, and nearly all researchers and security practitioners that I follow. Big thanks for the organizers, Positive Technologies, for such an amazing opportunity!

It is also a truly international event. You can see speakers from all over the world. And all information is available both in Russian and English. Almost all slides are in English. Three parallel streams of reports, workshops and panel discussions were dubbed by professional simultaneous interpreters, like it is a United Nations sessions or something, recorded and broadcast live by the team of operators and directors. Final result looks really great.

Video of my presentation:

I was talking too fast and used some expressions that was hard to translate. The translator, however, did an awesome job. He is my hero! 🙂 If you didn’t understand something on video, I made a transcript bellow.

A version without translation for Russian-speakers is here.

Slides:

Unfortunately gif animation is not working in the Slideshare viewer.

Today I would like to discuss vulnerability databases and how vulnerability assessment systems has been evolving. Prior to discussing vulnerability databases I need to say that any vulnerability is just a software error, a bug, that allowing hacker to do some cool things. Software developers and vendors post information about such vulnerabilities on their websites. And there are tons and tones of vendors, and websites, and software products, and vulnerabilities.

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Why you can’t update it all at once?

It’s the second part of our talk with Daniil Svetlov at his radio show “Safe Environment” recorded 29.03.2017. In this part we talk about vulnerabilities in Linux and proprietary software, problems of patch an vulnerability management, and mention some related compliance requirements.

How critical these vulnerabilities are? Are they really exploitable in our infrastructure?

Video with manually transcribed Russian/English subtitles:

Previous part “Programmers are also people who also make mistakes”.

Taking about the fact that if you use fully updated software and do not use some self-written scripts, programs, then in theory everything will be safe.

But recently there was some statistics that critical vulnerabilities stay in Linux kernel about 7 years from the moment they appeared as a result of a programmer’s error till the moment they were found by our white hat researcher.

But it is not clear during these seven years if cybercriminals have found them, used them and how many systems were broken using this vulnerabilities. Not to mention that some special government services may use it too.

For example: The latest Linux kernel flaw (CVE-2017-2636), which existed in the Linux kernel for the past seven years, allows a local unprivileged user to gain root privileges on affected systems or cause a denial of service (system crash). The Hacker News

Well yes. There is such a statistic. There is also some criticism from proprietary software developers. Like you say “many eyes that looks in code will find any error.” This is a quote from Linus Torvalds, if I’m not mistaken.

Not exactly. Linus’s Law is a claim about software development, named in honor of Linus Torvalds and formulated by Eric S. Raymond in his essay and book The Cathedral and the Bazaar (1999).[1][2] The law states that “given enough eyeballs, all bugs are shallow”; or more formally: “Given a large enough beta-tester and co-developer base, almost every problem will be characterized quickly and the fix obvious to someone.” Wikipedia

But in practice, yes, there are really old vulnerabilities that come up after many many years. Because apparently they did not looking for this vulnerabilities well enough.But we still don’t have anything else, except Linux kernel. Therefore, they can say anything, but they will use it anyway. It is in the first place.

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ZeroNights16: Enterprise Vulnerability Management

17-18 November I was at the great event  Zero Nights security conference in Moscow. For the first time as a speaker. Being a part of such famous and prestigious security event was very exciting. There were three of us, Ekaterina Pukhareva, Alex Smirnoff and me, and only 20 minutes available for all. I was talking mainly about VM solution problems and custom reporting/ticketing, Ekaterina shared some experience in using Tenable SecurityCenter for Vulnerability and Compliance management, and Alex was talking mainly about Asset and Risk Management.

Alex ArkanoiD Smirnov, Alexander Leonov, Ekaterina Pukhareva at ZeroNights 2016

Presentation was recorded and some time later video will be available on YouTube. However, I suppose audio will be only in Russian not earlier than February 2017. So I think it will be a much more useful to share some points of the presentation right now. Lucky here I don’t have any time restrictions. =)

The first thing to say about Vulnerability Scanners and Vulnerability Management product is that there are plenty of them. On this picture I mentioned some of the products/vendors.

Vulnerability Scanners and Vendors

Some of them are highly specialized, like ErpScan for SAP, others are universal. Some of them are presented globally: Tenable Nessus / SecurityCenter, Rapid 7 Nexpose, Qualys, F-Secure etc., others are known mainly in Russia: Positivie Technologies Maxpatrol, Altx-Soft RedCheck, Echelon Scaner-VS. Some products are expansive, some of them not and even have versions available for free: OpenVAS, SecPod Saner Personal, Altx-Soft ComplianceCheck, Qualys SSL labsHigh-Tech Bridge SSL Server Security Test, etc.

In my opinion the main problems of VM solutions are expansiveness and low reliability of the scan results.

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Fast comparison of Nessus and OpenVAS knowledge bases

In my opinion, quality of knowledge base is the most important characteristic of Vulnerability Management (VM) product. Maybe it’s because I have spent significant amount of time making different security content for vulnerability scanners and this is some form of professional deformation. 🙂 The fact is that nowadays we have dozens of VM solutions on the market, which have very different knowledge bases and thus different abilities for detecting vulnerabilities. And really nobody talk about this. I can recommend related post “Tenable doesn’t want to be Tenable anymore” and especially HD Moore’s comment to that post. It describes the reason why nobody interested now in quality of detection. Maximum what we, end-users, can hear from the vendor about it’s knowledge base is an amount of vulnerability checks: 40000-80000 and approximate list of supported systems. There is a massive false belief that detection quality of the products is approximately the same and it’s better talk about dashboards, reports, SIEM-like capabilities. To demonstrate that the difference actually exists I made a pretty primitive comparison of Nessus and OpenVAS knowledge bases.

I chose these two products, mainly because information on their NASL plugins is available at Vulners.com. As I also wrote earlier how you can use easily parse Vulners archives in python, so you can repeat it for yourself. I talked about this topic at Pentestit webinar about Vulners. If you are familiar with Russian, you can also check this out. 😉 The slides for this presentation are available here.

Why I call this comparison fast and primitive? I don’t define the structure of KBs for this product and don’t carefully map one nasl script to another. I suppose it may be a theme for another posts. Instead I am looking at the CVE links. If two scanners detect can the same vulnerabilities, they should have the same CVE links in all the NASL scripts, right? In reality we have a great difference between the products and more than a half of the CVEs can’t be detected by using both of them.

CVE links from NASL plugins

All CVEs: 80196
OpenVAS CVE links: 29240
Nessus CVE links: 35032
OpenVAS vs. Nessus: 3787;25453;9579

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