Introduction
I like YARA. I constantly chuckle when I hear its name and feel the want to speak German. For those who are curious, its origins are a little further south and on a different continent, specifically South America.
It never ceases to amaze me how many clever people in our industry haven’t used it or, in some cases, even heard of it. YARA is a tool designed to help malware researchers find and categorize malware samples, among other things.
It has been around for a long and is backed by a thriving, growing community. It is tough to outperform its price because it is an open-source software written in raw C and supplied for free through Github.
How does it function?
That’s easy to explain, I suppose. YARA provides a profusion of pattern-matching capabilities. It may be a sniper zeroing in on a single target, or an army of soldiers marching across a battlefield while forming shields.
Whether done with pinpoint precision or broad brushstrokes, both are realistic depictions of its detection capabilities.
We used to joke that YARA was so skilled at finding stuff that it drank napalm and ate artillery shells. It’s also as smart as you make it, thanks to user-generated logic.
More YARA devotion
You could still be confused about what it is. On the one hand, YARA is a lightweight, versatile tool that can work with virtually any operating system. Because the source code is freely available, it is simple to change or expand it to meet a specific use case.
YARA is a simple tool to use for digital forensics, incident response, and reverse engineering. YARA, on the other hand, is your bloodhound. It enjoys finding, spotting, and solving logical riddles.
Its targets are the normal files that come to mind when thinking about files binaries, documents, drivers, and so forth. Network traffic, data repositories, and other things that you might not expect to be scanned are examples.
It may come as a surprise to you that it can be used by your SIEM, triage tool, phishing, sandbox, or IDS. Many technologies have it quietly woven into their fabric. When you find out about YARA, it is usually after the fact.
YARA can be run from the command line on Linux and Windows while working locally for incident response or reverse engineering. You may easily get it online by starting it in the terminal. You can also put it to use right away by giving it logic and a goal.
It doesn’t get much praise for its graphics and, to be honest, doesn’t attempt. It gains more from using Python, Ruby, Go, and other bindings that integrate it with graphical applications or wrap it in an API.
The reasoning that makes up YARA’s brain is just as efficient and clear. YARA accepts input via the terminal or a simple text file providing logic. Its Ying/Yang is just true or untrue, and it thinks in patterns created by rules. The rules are straightforward.
You provide the name, matching items, and matching pattern. You can either derive a pattern and look for targets that satisfy the logic, or you can produce the rule from a target by analyzing it from the inside out and looking for matches.
YARA: Why would you use it?
YARA appears simple and it is but it has a vast range of uses. I could go on and on about its capabilities, but it seems unfair not to discuss how it is put to use.
Its usage in reverse engineering may be the simplest to describe. If you reverse engineer malware without using it, you will miss out on a fast triumph that will speed up your productivity.
Matching files based on attributes, classifying files into families, identifying algorithms, detecting code caves, code stomping, and other simple applications are available.
Is there an emergency response? There is no problem. You finally start evaluating files to see how they connect to the situation that generated your response. YARA then enters the picture, either to function as any virus that may be there or to quickly seek out and discover items of interest.
If you collect file intelligence of any type or run a lab that analyses files of interest, YARA can be a big workhorse in the process. Any attribute of a file can be located and recognized, including those left behind by the compiler, composer, or cracker.
As previously indicated, a file’s structure, as well as the containment and order of its contents, comprise genuine bundles of intelligence that can be harvested with the correct reasoning.
The examples above are pretty self-contained, but yara labs also excels as a support and follow-up tool. Do you deliver papers to sandboxes? If this is the case, it has the potential to improve the findings and knowledge received from the sandbox file explosion.
The same is true if you use it in your email filter, phishing detection system, or SIEM, all of which are supported by Alienvault.
Conclusion
YARA is adaptable, strong, and widely available. It has a low learning curve and many applications. In a world where your adversary hides in plain sight and around the corner, it has extraordinary detecting skills to throw light on the suspicious, harmful, or simply interesting. If it hasn’t already found a place in your toolkit, it’s time to take action and make it happen.
