Random Thoughts, Security Learning, What you need to know?

SIEM Use Cases – What you need to know?

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My previous post “Adopting SIEM – What you need to know” would give a better starting point if you are new to SIEM and want to implement it in your organization. If you already use/manage/implement a SIEM, then read on.
To start with, SIEM tools take a lot of effort to implement. Once implemented, they need to be taken care like babies. If care is not given, within a few months you would be staring at a million dollar museum artifact. Now there are two parts of care:

  1. Making sure that the systems are updated regularly, not only for patches and configurations but also the content put in them.
  2. Second and the most important part is making the SIEM relevant to the current Threat Landscape.

Anyone who has worked on SIEM for some time would agree with me, that Administration is generally easier compared to making the system relevant to the Threat Landscape. Before people hit me with “Administration is also a pain”, I would like to offer a defense saying that mostly, all SIEM products have documentation attached that give fair amount of information on how to install, update, upgrade and operate these systems. However, Translating Threat Landscapes to nuts and bolts for SIEM purposes is the biggest challenge and there are no guides that can help do that.

In this blog post, my attempt is to make this translation as easy as possible. In SIEM parlance, we call the translation as a Use Case. If there is well-defined Use Case, implementing them, responding to them and managing them would become easier. Such Use Cases would eventually become the cornerstone on which a SOC (Security Operations Center) is built. As usual, I would like to start with defining a Use Case, running through its stages and then finally wrapping it up with an example. So here we go.

Use Case Definition: A Use Case by definition is nothing but a Logical, Actionable and Reportable component of an Event Management system (SIEM). It can be either a Rule, Report, Alert or Dashboard which solves a set of needs or requirements.

A Use Case is actually “developed” and this development is a complete process and not just a simple task. Like a mini project it has several stages. The various Stages involved in Use Case Development are as follows:

  • First stage is the “Requirements”Definition. It can be any of the following high level requirements and is unique to every company:
    1. Business
    2. Compliance
    3. Regulatory
    4. Security
  • Once the requirements are finalized, the next stage would be to “Define the scope” of the requirement. This would typically mean the IT Infrastructure that needs to be protected and is a high priority for the specific requirement.
  • Once the scope is finalized, we can sit down and list the “Event Sources” that would be required to implement the Use Case. These would be Log Data, Configuration Data, Alert Data etc coming out of IT Systems under the above Requirements Scope.
  • The next stage would be to ensure that the Event Sources are going through “Validation Phase” before use. Many times, we would have an Event source but the required data to trigger an Event may not be available. This needs to be fixed before we proceed with the Use Case development.
  • Post validation, we need to “Define the Logic”. This is where we exactly define what and how much data is needed to alert along with the Attack Vector we would like to detect.
  • Use Case “Implementation and Testing” is the next stage. This is where we actually configure the SIEM to do what it does best – Correlation and Alerting. During Implementation the definition of the desired output can also be done. The output can be one of the following:
    1. Report
    2. Real Time Notification
    3. Historical Notification
  • Once implementation is done, we need to “Define Use Case Response” procedures. These procedures help you to make the Use Case Operational.
  • Finally, Use Case “Maintenance” is an ongoing process to keep the Use Case relevant by appropriate tuning.

Now that we have defined in detail the Use Case Development methodology, it is time to take an example and see how this actually looks in Real Life Implementation terms.

The Requirement: Outbound Spam Detection.
The Scope: Mail Infrastructure, End User Machine, Security Detection Infrastructure
The Event Source:
  • IDS/IPS at Network and Host – Signature Based Detection
  • Mail Hygiene or Mail Filtering Tools – Signature Based Detection
  • Events from Network Devices – Traffic Anomaly Based Detection
  • Events from End User Detection tools – Signature and Traffic Anomaly Based Detection

The Event Validation: The devices logging to SIEM should be normalized and parsed properly. Typically, SIEM products would allow Content development based on their native Field Mappings (Through Parsing). If the fields are not mapped, then the SIEM does a poor job of Event Triggering and Alerting. The required fields for the above Use Case would typically be Source IP, Source user ID, Email Addresses, Target IP, Host information of Source and Target, Event Names for SPAM detection, Port and Protocol for SMTP based traffic detection etc.

Use Case Logic Flow: The Logic definition is something unique to the environment and needs to be defined accordingly. The logic can be either Signature based or behavior based. You can have it restricted to certain subset of data (based on the Event Sources above) or expand it to be more generic. Some samples are given below:
  • One machine doing Port 25 Outbound connections at the rate of 10 in a minute
  • SPAM Signatures originating from the same source from IDS/IPS, Mail Filter etc having the same destination Public domain
  • SYN Scans on port 25 constantly from a single source etc

Implementation and Testing: Once the logic is defined, Configuration of SIEM and tuning the implementation to trigger more accurately is the next phase. After Implementation of the Use Case, we would need several iterations of Incident Analysis along with data collection to ensure that the Use Case is doing what it is intended to do. This is done at the SIEM level and may involve aggregation, threshold adjustments, logic tightening etc.

Use Case Response: After implementation, the Use Case need to be made as a valuable resource by Defining a Use Case Response. This is the stage where you would define “What action needs to be taken and how it needs to be taken”. You can look at Episode 4 of my Security Investigation series to get an idea of how to Investigate SPAM cases. Other Security Investigation Series Articles are located here – Security Investigation Series.

SIEM Use Cases are really the starting point for good Incident detection. If you want to run a SOC, having well-defined SIEM Use Cases would ease management and increase efficiency of Operations. This post is my humble attempt to simplify and regularize Use Case development for SIEM implementations.

As always, I would love to hear comments and thoughts on this topic.

Security Investigation Series

Episode 4: Security Investigation Series – Tackling SPAM Attacks

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One of the age-old attacks seen in the Internet is a SPAM attack. Many organizations have been blacklisted for having been a SPAM relay or a SPAM Source. Even though technologies have improved vastly over the decade, SPAM is still real and users are still being enticed by SPAM. The result is Machine Compromise and potential data breach. As of 2011, more than 7 Trillion SPAM Messages have originated. Many organizations combat SPAM in many different ways. In this Security Investigation Series Episode, I am going to layout a workflow for SPAM detection, Cleanup and Prevention.

Understanding SPAM: Firstly, let us understand SPAM. SPAM is nothing but a mass of unsolicited messages being sent anonymously or using fake identities. This often is a pre-cursor of an attack and hence is one of the Attack Vectors.  Two major sources of SPAM in an enterprise are

  • Email based SPAM and
  • Instant Messaging SPAM

Let us break this down even further. Email based SPAM uses SMTP protocol as its transport whereas the Instant Messaging using a gamut of protocols from HTTP, SIP, IMPP to XMPP. Several tools and technologies for SPAM detection and filtering work at this protocol level and identify SPAM and filter them as needed. Still intelligent spammers, can circumvent the detection and make their way to the user mailbox. In such cases, a clear incident detection and response process is needed.

Let us take one sample scenario so that I can layout the process flow for similar scenarios.

A Real Life Scenario: A mail is received at the user’s inbox containing a Password Stealer link. This is suspected as SPAM by the Security Devices in your enterprise. The security devices can be anyone or combination of Intrusion Detection Systems, Gateway Filters, SPAM filters etc. These alerts are logged to a SIEM solution. SIEM Solutions then correlate the various messages received and trigger an Incident. If there are no Security devices that do this, SIEM can help you identify SPAM through Network Traffic monitoring.

Logic for good SPAM detection: In signature based detection, it is good enough to just pick on the Triggers from the individual product vendors and then correlate among them. But if there is a SPAM message that is fresh and does not have a signature pattern, then only behavior based detection will be effective. Several tools today do some behavior based detection. Enterprises who don’t have behavior based systems can look at making use of SIEM to be that system. SIEM is a powerful tool and can do trending, correlation and pattern matching. A simple rule can be written for network log correlation for protocols like SMTP/IMP etc. Typically a value of 25 SPAM messages going to different destinations within a minute is a good indication of SPAM. This value combinations can be throttled (Throttling is a great SIEM topic and one of the classic rule writing as well as throttling ArcSight example can be found here at wymanstocks.com) to get a more accurate SPAM detection rate. This detection is crucial for the response to be triggered.

Responding to SPAM Attacks: Once the SPAM detection is done through signature or behavior based logs, it is important to take a series of responsive actions.

  • Before responding obviously validation needs to be done to ensure we don’t falsely respond to a legitimate email. This is typically done at the SIEM level itself and is the job of a Level 1 Analyst.
  • Then, We need to ensure that the SPAM domain is blocked at the gateway level. This is to ensure that the SPAM does not spread from Internal to External. Some SPAM mails have carefully constructed callback to the domain itself and hence it is important to block it at the gateway.
  • Secondly, we need to ensure that the SPAM spreading is controlled in the Internal Mail Infrastructure. This can be done by putting filtering rules in Exchange to move SPAM messages to the deleted items folder. Similarly for IM also, such rules can be put in the messaging server.
  • Finally, the SPAM has to be cleaned from the individual machines. This is where it gets interesting.
  • There are three major types of users:
    1. Many users are aware of the SPAM and hence they would not have clicked on any of the links available in the mail or the message. These user machines can be remediated by just deleting the SPAM messages.
    2. Some users who are curious would have clicked on the link and then closed it after seeing its suspicious face. Majority of these cases are nothing and get remediated by just deleting the SPAM message. Some targeted SPAM attacks work to just make the user click on the SPAM link and then get re-directed to a Malware Dropper site. In these cases, even though the SPAM mail has been deleted the users are at risk. Hence these user machine have to be validated as well for possible compromise.
    3. Time and again we also see users clicking on the link, keying in all their data to the site and then feeling that nothing wrong has happened to them. These user machines are no longer clean and have to be re-imaged straight away.
  • Once the remediation is done, the appropriate documentation need to be carried out. Again as I said, documentation is vital in a Security Investigation process. Without documentation, it will not be repeatable, it will not be efficient.

Preventing SPAM Attacks: Preventing SPAM is the ultimate goal for every enterprise. Day in and Day out, Enterprise Defenses are being improved to combat SPAM. However, SPAM is mostly an initialization vector and hence it is at the hands of the End-User to be aware of the risks involved with SPAM. So more than the tools and technologies I would say “User Training” is the best way to prevent SPAM. What do you think?

How do you combat SPAM in your enterprise? Sound off in the comments below

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Random Thoughts, Security Learning, What you need to know?

Adopting SIEM – What you need to know?

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“SIEM stands for Security Information and Event Management”

Oh wait, I have heard of SIM, I have heard of SEM, what is this SIEM??.
Originally, the Security Information Management (SIM) and Security Event Management (SEM) systems were two different technologies performing similar but distinct functions. Gartner in 2005, coined the term SIEM to encompass both. As the name suggests, It is nothing but a collection of tools and technologies to manage Incident and Events pertaining to Security alone. Some of the tell-tale capabilities of a typical SIEM platform are:

  1. Collect Logs from various Log Sources/Devices
  2. Store these logs for a decent amount of time
  3. Provide Fast Search/Retrieval capabilities
  4. Provide meaningful interpretation of Log received
  5. Provide capabilities to correlate between logs of different devices
  6. Basic Ticketing/Alerting capabilities.

The first 4 points are typical of a SIM and the remaining 2 are typical of a SEM.
Any tool that does all of these is a SIEM. There are more than 50 different products that cater to the SIEM space. Just like any other product, they cater to various market segments at various price points.
If you Google for SIEM reviews you would get a lot of information on various products. In my experience, I have worked with at least 4 SIEM vendors. Each one of them have their own pros and cons. Comparing a product in a DEMO and comparing it after use are two different things. So, in this blog post, I am going to highlight few things as “What you need to know” when you are planning to adopt SIEM technology

  1. Have a defined Logging process in your environment. This is very crucial because a SIEM is useless without a good Logging Program. This not only helps in making the SIEM implementation easier, but also helps in getting a measure of the volume you are dealing with. In my experience, often times, despite having an Industry leading SIEM, the log Management made it look pedestrian and a waste of money.
  2. Every SIEM vendor has something called as Collector/Connector/Receiver/Agent that collects logs from the devices and converts them to their proprietary format. This conversion or parsing as we call is important for the product developers to store data in a format they can understand and process quickly. Most of the vendors offer something of a Custom Collector/Parser development for their “unsupported” log sources. This costs money, skills in-house and may require regular maintenance. Hence Native Parsing Support for Log Sources is better. Establish this before you move ahead with SIEM implementations. Either source a in-house resource to help build and manage such customizations or spend more money to get the vendor to do it.
  3. Identify primary focus areas from an Organizational perspective. This will help you configure your SIEM solutions appropriately. These focus areas should be broadly classified and then expanded to the ground level. For example, if your requirement is compliance, start with control requirements, see what logs need to be collected to fulfill them, see how integration needs to be done, see what needs to be reported, alerted, retained, etc.
  4. Get a dedicated SIEM administrator or rather train someone in-house to be that person. This is very important because, in my experience I have always felt that SIEM is as good as the administrator is. Without proper maintenance and care, it will decay over time. If you really need to generate value out of it, manage it well. By managing a SIEM I mean not only the system itself but also the ecosystem it resides in.
  5. Understand that SIEM alone cannot solve all your Security Problems. It is NOT A MAGIC WAND. If setup and configured correctly, a SIEM can at best point you in the right direction, a direction where you can identify and fix several security issues in your enterprise thereby strengthening it. So, be prepared to have a Response/Remediation team that will investigate the alerts generated and take appropriate action.
  6. Correlation is a vital part of SIEM offerings. Before Adopting SIEM, make sure you understand and possibly catalog the various Attack Vectors, Threat Scenarios you would want looked at for correlation in your organization. This will give a fair direction for the basic rules you would put in place to start with. Once you are comfortable and start seeing the various alerts generated, you can play around and experiment more. In my experience, start with built-in rules, understand them, investigate them, tune them and then slowly start building your own content. For more details on the various rules available in SIEM Look at Rules Rule in SIEM Kingdom
  7. Architecture wise, make sure your SIEM solutions are in tandem with your Logging solutions. Also, build your SIEM as modular as possible thereby making upgrades, technology refresh etc seamless.
  8. Don’t forget the filtering aspect. Correlation Engines will perform faster and will get you better results if they are attacking a smaller set of “known bad” logs rather than all. This is crucial in large enterprises as the Log Volume can easily overwhelm the SIEM systems. Note: Many SIEM tools have limitations in the number of events they can process. This is denoted in Events Per Second (EPS). Even though the vendors advertise several thousands, an effective correlation system can have only around 2000 – 5000 EPS tops. Anything more will make your system painstakingly slow. So understand and work through this. Look at my posts What and How much to Collect and High Log Volume – What to Filter and What to Keep? to get more information on how to log, what to log and what to filter.
  9. Remember, more processing layers, less EPS. This means that the Log Collection layer will have more EPS processing capability than the Correlation engine and so on. Visualize it as a pyramid with the Log Collection at the Base and the Correlation at the top
  10. Last but not the least, “Stay Alert and Eager. The Logs Don’t Lie”

Hope this post helped you in getting a fair idea of SIEM technologies. I have worked on HP ArcSight, Symantec SSIM, Novell E-Sentinel. If you need details about them in terms of practical setup, configuration, architecture etc, shout out and I will help as much as possible.
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