Introduction
Historically, leveraging shared threat intelligence for malware detection has presented significant challenges to security teams. These challenges stem from the ever-evolving nature of malware threats, as well as the need for timely and accurate intelligence sharing among relevant parties.
Traditional hash-based indicators, which rely on precise matches, frequently fall short against advanced attackers and automated malware generation toolkits. A single modification to the malware can render these indicators ineffective by evading signature-based detections. Hash-based detection is only effective for identifying known malware samples. It cannot detect new variant of a prevalent malware.
Bad actors can achieve bypassing hash-based detection (aka. reputation or blocklisting or allowlisting) with minimal changes without altering the code itself. All they need to do is add a new timestamp, and that will be sufficient to evade hash-based detection. In other words, a simple tweak will allow them to get around hash-based detection.
To enhance the detection of malicious files, security professionals can prioritize the recognition of malware families, which are groups of malware that have common code but are not identical. YARA (Yet Another Recursive/Ridiculous Acronym) is a tool that specializes in this type of matching and has become an industry standard within the malware analysis community.
YARA rules serve as a potent instrument for security professionals to detect and categorize malware families. YARA rules can be applied to scan files located on disk, memory, or within network traffic, allowing for malware detection at various stages of an attack. Utilizing straightforward yet efficient patterns, these rules scan files and process’ memory active on the system. This enables the identification of both known and evolved malware families, making YARA an invaluable asset for detection engineers, threat researchers, and DFIR analysts.
Moreover, YARA rules can be combined with other tools like sandboxing, intrusion detection systems, and threat intelligence platforms for a more robust detection mechanism. Its ease of use and open-source nature make YARA a favored option among security professionals across different sectors. As malware continues to grow in sophistication, employing tools like YARA rules becomes essential in detecting and thwarting malware attacks.
Decode Malware Mysteries with YARA Rules and Sandboxing
Threat actors often use a combination of various methods to avoid being detected and analyzed by anti-virus, static analysis, and dynamic analysis tools. One commonly employed tactic is to compress, encrypt, and/or obfuscate malicious files, making it more difficult and time-consuming to identify and categorize the malware and address the associated threat. However, to function as intended, the malware must be restored to its original state in memory in order to execute. This presents an opportunity to detect potentially malicious behavior and classify it within the isolated environment of a malware sandbox.
Once you craft a new YARA rule, you can scan your environment (Windows, Linux or MacOS) with it since many Endpoint Detection and Response (EDR) tools provide YARA support. You can also upload it to VirusTotal for LiveHunt or RetroHunt. In either case, if there’s a pattern match, you can submit the suspect file to the sandbox to double-check it’s not a false positive and extract the IOCs and the malware configuration. With the help of a sandbox, you can create new YARA rules based on the malware’s sneaky actions, including network artifacts, memory dumps, dropped files, registry keys, runtime strings etc. Another option is to take advantage of the built-in YARA rulesets classified by malware type.
For those who are already familiar with our products, DeepResponse, FinalVerdict and TotalInsight, in addition to these primary functionalities, a separate set of YARA rules are used to trigger memory dumps. When used in parallel with VMRay’s multi-layered analysis engine, security teams can use this valuable output in threat-hunting scenarios as well as incident response. To learn more about how smart memory dumping can be, check out this blog post from our LABS team.
Let’s delve into the hurdles of YARA rules.
Tackling YARA Rule Challenges for CTI Analysts: A Smoother Workflow
It’s beyond dispute that YARA rules play a crucial role in the daily workflow of Threat Intelligence Analysts. For the longest time, MISP has also had the capability to facilitate the exchange of pre-crafted YARA attributes on top of IOCs. Although it’s widely recognized, they also present challenges when it comes to collaboration, scale, and management. This is particularly true in large organizations where coordinating detection engineering efforts between various teams can be daunting.
In large organizations, one of the main challenges is collaboration on YARA rules and sharing results across multiple teams. Issues such as version control can make it difficult to maintain multiple versions of the same rule or track changes made by different individuals. Ensuring proper access control for sensitive YARA rules and integrating rules developed by various team members into a unified set can be time-consuming. Validating the accuracy and effectiveness of rules written by different individuals also poses challenges.
Moreover, organizing, updating, and maintaining YARA rules effectively can be a daunting task for CTI analysts. Factors such as rule volume, accuracy, priority, sharing, documentation, and performance all contribute to these challenges. Keeping a large number of YARA rules up-to-date and accurate as the threat landscape evolves can be difficult, particularly when dealing with false positives and rule evasions. Although YARA rules are meant to be resilient to changes, this form of signature-based detection has its limitations when there are too many alterations to the critical areas that should be covered by YARA. In other words, while YARA rules are useful, they can only go so far, and ongoing maintenance and updates may be necessary to cover all the bases.
Determining the priority of YARA rules, ensuring the most important ones are updated and maintained first, and sharing rules among different teams within an organization can be problematic if there is a lack of standardization or collaboration tools.
Another issue Detection Engineers face is documenting YARA rules and monitoring their performance which is crucial for maintaining accuracy, consistency, and scalability. Tracking the reasons for creating each rule helps ensure they remain relevant over time, while closely monitoring their performance ensures they run efficiently.
Despite these challenges, YARA rules are still valuable tools for enhancing security solutions. To minimize these hurdles, open-source tools like Synapse from the Vertex Project can be utilized to overcome the challenges associated with YARA rules. By leveraging such resources, organizations can effectively manage and deploy YARA rules to detect and categorize malware families, even when the specific variants have not been seen before.
Final Thoughts
In a nutshell, fighting against malware is a never-ending battle that requires constant adaptation and innovation from security professionals. While traditional hash-based detection methods have limitations, YARA rules offer a powerful way to identify and categorize different malware variants. By creating your custom YARA rules, you can shield your organization from these evolving threats. You can combine them with other detection mechanisms and sandboxing for an even stronger defense against malware attacks.
YARA rules play a critical role in the daily workflow of Threat Intelligence Analysts, but managing and organizing them effectively can present significant challenges in large organizations. With proper standardization, collaboration tools, and ongoing maintenance, YARA rules can continue to be a valuable asset in the fight against evolving malware threats.
So, let’s stay ahead of the game, be proactive, and keep those bad actors at bay.
Latest news from the YARA community
As YARA rules have become indispensable for detecting and analyzing malware, the community’s dedication to innovation and collaboration has led to the recent release of several powerful tools.
Here are some updates from the YARA community:
- Yara 4.3.0 has been released.
- To disrupt Cobalt Strike abuse by threat actors, Google released 165 YARA rules for Cobalt Strike.
- Malware Researcher Florian Roth published a new tool named “yaraQA” to analyze YARA rules.
- Christian Blichmann from Google built a tool to automatically generate AV byte signatures for YARA.
- Didier Stevens published an update on the Windows version of YARA, which did not include a new feature named ‘–skip-larger’ enabling skipping files above a certain filesize threshold in a scan.
- abuse.ch has published a new tool called ‘YARAify’ that includes a large set of YARA rules, enabling users to scan files online. Essentially, ‘YARAify’ is a central hub for scanning files and threat hunting, and the fact that it is community driven is a huge advantage. As long as the community remains, the tool will enhance itself, and as a result, the community will benefit from the tool even more.
