MISP YARA Rules

A brief refresher: What are YARA rules?

YARA rules are used to detect and classify files based on fragments of binary or text data. They're especially useful for identifying malware.

Let's look at a simplified example of a YARA rule and examine what each part does:

In this example, the YARA rule will search for both strings $a and $b in the file, and the rule will match only if both $a and $b are present.

This is a simplified example, but YARA rules have powerful pattern-matching capabilities that can overcome evasion tactics like obfuscation, encryption, and polymorphism. Rules can target unchanging traits like metadata, file headers, and behaviours that malware can't easily disguise without breaking functionality.

Why is it useful to get YARA rules from MISP?

While YARA rules are frequently shared in public Github repositories, that doesn't easily give you the power to send the rules to your automated systems, or share them with other people.

That's why YARA rules in MISP are so powerful: they can be sent to your automated systems, like SIEM tools, or shared with other teams and organisations.

Malware is constantly evolving, with new malware released every day. Having the newest YARA rules automatically pulled into MISP, ready to be deployed wherever you need them, is one of the capabilities that makes MISP so useful.

(By the way, if you're not using MISP yet, or are using it already and finding it difficult to maintain, we offer a hosted, enterprise-grade MISP as a service called CloudMISP.)

Here are some of the most common detection systems that can be integrated with YARA rules from MISP:

• Antivirus
• IDS/IPS systems
• SIEM platforms

How can I get YARA rules in MISP?

Two of our favourite sources for getting YARA rules in MISP are the CIRCL OSINT Feed and Feedly for Threat Intelligence.

CIRCL OSINT Feed
The CIRCL OSINT Feed includes many events with included YARA rules. It's one of the feeds included with MISP by default. To view only YARA events, you can filter events by type "yara".

Feedly for Threat Intelligence
Feedly automatically extracts IoCs from blog posts and news articles and can be configured to publish these extracted IoCs as a MISP feed. These feeds often include YARA rules, which are frequently shared online by malware analysts and researchers as part of their write-ups.

What can I do with YARA rules once they're in MISP?

Once you have YARA rules integrated and pulled into MISP, you can use them in several ways to enhance your threat intelligence and incident response capabilities:

1. Threat Detection

Use Case - Apply YARA rules to scan files, memory, or network traffic for malware or specific indicators of compromise (IOCs).

How to Do It

• Export YARA rules from MISP and use them with endpoint detection tools or file scanners like YARA CLI, VirusTotal, or custom scripts.
• Integrate YARA with SIEMs (e.g., Splunk, Sentinel) or EDR solutions to scan incoming data for matches.‍

2. Threat Hunting

Use Case - Proactively search your environment for signs of compromise.

How to Do It

• Deploy YARA rules to hunt across endpoints, file systems, or memory dumps using tools like Cuckoo Sandbox, Loki, or an EDR platform.
• Target specific file types or memory artifacts identified by MISP's threat intelligence to search for malicious activity.

3. Malware Analysis

Use Case - Analyse suspicious files or binaries to understand threats better.

How to Do It

• Use the YARA rules pulled into MISP for static analysis of files in sandboxes or isolated environments.
• Match YARA signatures against malware samples to identify variants or related campaigns.

4. Automation & Enrichment

Use Case - Enrich your MISP events and automate workflows.

How to Do It

• Tag MISP events with matched YARA rules to provide context about specific threats.
• Integrate MISP with security orchestration tools (e.g., SOAR platforms) to automate detection and response workflows using YARA rules.

5. Incident Response

Use Case - Support investigations during and after incidents.

How to Do It

• During an active incident, use YARA rules to quickly triage and identify malicious files or activities in your environment.
• Leverage rules to identify lateral movement or persistence mechanisms.

6. Sharing Threat Intelligence

Use Case - Collaborate with other organisations or teams.

How to Do It

• Share curated YARA rules with trusted partners via MISP to help them defend against similar threats.
• Export YARA rules enriched with context from MISP for use in broader threat-sharing communities.

Ready to get started?

If you're not using MISP yet, or struggling to get it working reliably for your team, we can get you up and running quickly with CloudMISP, our managed MISP instance. You'll be able to ingest and use YARA rules in MISP within a few days of signing a contract.

If you're already using MISP but need help ingesting and integrating YARA rules with your automated systems, we can help. We are experts in integrating MISP with SIEM and EDR tools to improve your automated threat hunting capabilities.

‍Contact us to speak with a MISP expert