Reader Questions on Network Security Monitoring

A regular blog reader and Network Security Monitoring practitioner sent me these questions last month, so I'd like to answer them here.

1. Are all alert data created equal?

This question originates with my employment at an MSSP where we process many types of alert data from Dragon IDS, Cisco IPS and ISS. Snort and Sourcefire strangely are underrepresented. My question is if Dragon IDS, Cisco IPS, ISS, Snort and Sourcefire all looked at the same full-content data, would they all produce the same results? I think not and would like to empirically verify this theory.

Testing detection systems is a complicated topic. I am not sure what methodology a place like NSS Labs uses. I bet they get varying results depending on the product. If you read A Tool for Offline and Live Testing of Evasion Resilience. in Network Intrusion Detection Systems you will see big differences between Snort and Bro, for example.

2. When is an analyst no longer an analyzer of data but an analyzer of dashboards?

This question also originates with my employment at an MSSP because like I said, we process so many disparate alert types and there is only so much time in a shift that it is challenging for an analyst to really spend quality time with a piece of data and conclusively determine what happened. Therefore the analysts evolve into analyzers of dashboards instead of data in order to promptly assess alerts and determine if there was a legitimate attack or not.

I would say you are an analyzer of dashboards when you cannot do the following:

  • Determine how a product generated an indicator

  • See the underlying activity that produced the indicator, whether it is network traffic or raw log messages

  • Research activity for which there is no indicator, i.e., you can only see indicators and not any activity for which an alert did not fire



3. If all you have is alert data, can you positively confirm that you have been compromised?

I know the answer to this one, but am including it for emphasis of the point that alert data alone does not lend itself to digital situational awareness. Alert data + session data is the bare minimum as far as I am concerned. At least with this combination you can observe the egress sessions, in other words, what did the attacker do next?

You are right. If you only have alert data, you cannot validate a security incident.

Thank you for your questions!

Richard Bejtlich is teaching new classes in DC and Europe in 2009. Register by 1 Jan and 1 Feb, respectively, for the best rates.

Comments

Nathaniel Richmond said…
Richard, regarding point two, I strongly agree.

For determining how a product generated an indicator, I encourage anyone using commercial solutions to pressure the vendor for enough information that the alert criteria are transparent. For anyone evaluating a product, find out how much they will give you and consider it as part of your evaluation.

To use IDS as an example, some vendors may let you see signatures, some may after you sign a NDA, and some may not even with an NDA.

Seeing the underlying activity or researching when there is no indicator can be an issue with many network monitoring appliances since they have limited disk space for packet capture or do not include full session data. As a Sguil user, I've come to see anything less than full packet capture and session data as a compromise I don't want to make. Some situations may require compromising, but full packet capture and session data are amazingly useful.
10:16 AM
Anonymous said…
hey
your blog is very good
i invite you to visit my small blog
it's for security
you can give me your opinion on it
11:17 PM
Anonymous said…
What resources do you find most useful for staying on top of network security monitoring trends? We already have Tao Security on the list, but we're seeking more.
4:19 PM
Jim Sansing said…
I would enhance point 2 to read, "See sufficient context of the underlying activity, including both the request and the response, that produced the indicator, whether it is network traffic or raw log messages". If your IDS does not currently provide this, check out the Realeyes IDS at http://realeyes.sourceforge.net/. I have recently built new downloads and created live demos, which can be found on the Technology page.

Later . . . Jim
2:42 PM
Post a Comment

Popular posts from this blog

Zeek in Action Videos

Image
This is a quick note to point blog readers to my Zeek in Action YouTube video series for the Zeek network security monitoring project .  Each video addresses a topic that I think might be of interest to people trying to understand their network using Zeek and adjacent tools and approaches, like Suricata, Wireshark, and so on.  I am especially pleased with Video 6 on monitoring wireless networks . It took me several weeks to research material for this video. I had to buy new hardware and experiment with a Linux distro that I had not used before -- Parrot .  Please like and subscribe, and let me know if there is a topic you think might make a good video.
Read more

MITRE ATT&CK Tactics Are Not Tactics

Image
Just what are "tactics"? Introduction MITRE ATT&CK  is a great resource, but something about it has bothered me since I first heard about it several years ago. It's a minor point, but I wanted to document it in case it confuses anyone else. The MITRE ATT&CK Design and Philosophy document from March 2020 says the following: At a high-level, ATT&CK is a behavioral model that consists of the following core components: • Tactics, denoting short-term, tactical adversary goals during an attack; • Techniques, describing the means by which adversaries achieve tactical goals; • Sub-techniques, describing more specific means by which adversaries achieve tactical goals at a lower level than techniques; and • Documented adversary usage of techniques, their procedures, and other metadata. My concern is with MITRE's definition of "tactics" as "short-term, tactical adversary goals during an attack," which is oddly recursive. The key word in the tacti...
Read more

New Book! The Best of TaoSecurity Blog, Volume 4

Image
  I've completed the TaoSecurity Blog book series . The new book is  The Best of TaoSecurity Blog, Volume 4: Beyond the Blog with Articles, Testimony, and Scholarship .  It's available now for Kindle , and I'm working on the print edition.  I'm running a 50% off promo on Volumes 1-3 on Kindle through midnight 20 April. Take advantage before the prices go back up. I described the new title thus: Go beyond TaoSecurity Blog with this new volume from author Richard Bejtlich. In the first three volumes of the series, Mr. Bejtlich selected and republished the very best entries from 18 years of writing and over 18 million blog views, along with commentaries and additional material.  In this title, Mr. Bejtlich collects material that has not been published elsewhere, including articles that are no longer available or are stored in assorted digital or physical archives. Volume 4 offers early white papers that Mr. Bejtlich wrote as a network defender, either for technica...
Read more