Understand the Power of YARA Rules

Understand the Power of YARA Rules

YARA is a powerful and flexible pattern matching tool. It runs from a command line on Linux and Windows, which is handy when you are working locally for reverse engineering or incident response. YARA is used by incident responders, threat hunters, and malware forensic analysts, and helps identify and classify malware samples. It is an open-source project written in C and free via Github.

 

What does YARA do?

Because YARA is extremely flexible, it can act as either a highly targeted sniper rifle or as field artillery. It can be targeted to find a specific file hash on a web server or to broadly detect a certain file type across multiple systems (think binaries, drivers, documents, even network traffic). Even better, YARA has been adopted by multiple security vendors, so you can use it in your SIEM, Sandbox, IDS, and phishing tools. Here is a list of vendors who support YARA:

https://virustotal.github.io/yara/

Who should use YARA and why?

Malware Analyst

If you are a malware analyst and spend a good portion of your time reverse engineering malware, YARA will dramatically improve your work efficiency specifically when doing static file analysis. You can use YARA rules to define text or binary patterns that will match a file or component of a file to quickly find malicious files in a large set of data. Then you can create a rule that determines which packer was used to compile the file. You can pivot with that information to threat hunt for all files that use that packer. YARA can also use file attributes to classify files into groups or families. 

Incident Responder

As an incident responder, you spend time parsing files to learn how they are related to the incident that created them. Take, for example, the case of analyzing SPAM emails: in the analysis process, someone will undoubtedly find a malicious macro exploit. YARA rules can be created to define the macro and then be used (with the help of a tool like Hipara) to search other endpoints for the same macro and identify other SPAM emails that share that macro.

Threat Intelligence Analyst

If you work gathering threat intelligence from community groups, vendors or open-source data, YARA becomes an invaluable tool. As you define common threat or vulnerability attributes based on your analysis, YARA’s flexibility allows you to describe those attributes in a rule that can then be used to search out a file, including source code, that contains the attributes. YARA rules allow you to make threat intelligence actionable for the entire security team.

RangeForce YARA Training Modules

YARA has been described as the Swiss army knife for any security professional. Although YARA has been around for some time, there are still many who do not know how to use it or understand its full capabilities. RangeForce offers four hands-on training modules that take the learner from the basics of installing YARA to advanced lessons where the learner is creating malware classification rules or even writing custom YARA rules based on strings or byte sequences. Here are RangeForce’s YARA Modules.

Security Tools – YARA Introduction 

Learn how to install and configure YARA on a Linux server. Cover the basic structures of a YARA rule, and learn about the YARA resources that are available to make your life easier. Create your first rule to analyze a suspicious file.

Security Tools – YARA Rule Generation

There are a lot of tools to help you use YARA. One is yarGen, created by Florian Roth. yarGen makes it easy to generate YARA rules. In this module, you use yarGen to generate a YARA rule, understand how metadata and string scoring can be built into those rules, and finally, learn some tricks to optimize the YARA rules you’ve created.

Security Tools – YARA Rule Management

This module introduces you to the YARA-related repositories. In both official and unofficial repositories, you will discover useful tools and rulesets, which make malware analysis and classification much easier. During the completion of the objectives, you will learn how to download commonly available YARA rules and apply them for your specific purposes.

Security Tools – YARA Rule Writing

In this advanced YARA Rule Writing Lab, you can dig deeper into custom rules based on strings and byte sequences. Using different malicious file samples, this module will teach you how to build complex YARA rules based on the attributes of those samples. It also takes you through methods of building conditional based YARA rules while you learn how to test the rules you create.

Conclusion

Once you complete our four YARA Rule Training Modules, you will have the skills to put this powerful malware classification and threat hunting tool to use. We recommend you join the growing number of YARA communities, learning for the rules they have created and sharing your creations with them. Also, we are always looking to improve our training and get new ideas on modules. Please leave us your feedback and ideas on new YARA modules.

Learn more about the RangeForce YARA Training Modules here.

 

YARA Communities