YARA is a tool aimed at (but not limited to) helping malware researchers to identify and classify malware samples. With YARA you can create descriptions of malware families (or whatever you want to describe) based on textual or binary patterns. Each description, a.k.a. rule, consists of a set of strings and a boolean expression which determine its logic. Let's see an example:

rule silent_banker : banker
{
    meta:
        description = "This is just an example"
        threat_level = 3
        in_the_wild = true

    strings:
        $a = {6A 40 68 00 30 00 00 6A 14 8D 91}
        $b = {8D 4D B0 2B C1 83 C0 27 99 6A 4E 59 F7 F9}
        $c = "UVODFRYSIHLNWPEJXQZAKCBGMT"

    condition:
        $a or $b or $c
}

The above rule is telling YARA that any file containing one of the three strings must be reported as silent_banker. This is just a simple example, more complex and powerful rules can be created by using wild-cards, case-insensitive strings, regular expressions, special operators and many other features that you'll find explained in YARA's documentation.

YARA is multi-platform, running on Windows, Linux and Mac OS X, and can be used through its command-line interface or from your own Python scripts with the yara-python extension.

Do you use GitHub for storing your YARA rules? YARA-CI may be a useful addition to your toolbelt. This is GitHub application that provides continuous testing for your rules, helping you to identify common mistakes and false positives.

If you plan to use YARA to scan compressed files (.zip, .tar, etc) you should take a look at yextend, a very helpful extension to YARA developed and open-sourced by Bayshore Networks.

Additionally, the guys from InQuest have curated an awesome list of YARA-related stuff.

• 0x101 Cyber Security
• Adlice
• AlienVault
• Avast
• BAE Systems
• Bayshore Networks, Inc.
• Binalyze
• BinaryAlert
• Blueliv
• Cisco Talos Intelligence Group
• Cloudina Security
• Cofense
• Conix
• CounterCraft
• Cuckoo Sandbox
• Cyber Triage
• Cybereason
• Digita Security
• Dragos Platform
• Dtex Systems
• ESET
• ESTsecurity
• Elastic Security
• Fidelis XPS
• FireEye, Inc.
• Forcepoint
• Fox-IT
• FSF
• Guidance Software
• Heroku
• Hornetsecurity
• ICS Defense
• InQuest
• Joe Security
• Kaspersky Lab
• KnowBe4
• Koodous
• Laika BOSS
• Lastline, Inc.
• libguestfs
• LimaCharlie
• Malpedia
• Malwation
• McAfee Advanced Threat Defense
• Metaflows
• NBS System
• NetLock
• Nextron Systems
• Nozomi Networks
• osquery
• Payload Security
• PhishMe
• Picus Security
• Radare2
• RedSocks Security
• ReversingLabs
• Scanii
• SecondWrite
• SonicWall
• SpamStopsHere
• Spyre
• stoQ
• SumoLogic
• Tanium
• Tenable Network Security
• The DigiTrust Group
• ThreatConnect
• ThreatStream, Inc.
• Thug
• Threat.Zone
• TouchWeb
• Trend Micro
• UnpacMe
• Uptycs Inc
• VirusTotal Intelligence
• VMRay
• Volexity
• We Watch Your Website
• x64dbg
• YALIH

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