YARA
This is a tool designed primarily to aid malware researchers in identifying and classifying malware samples. It has become a staple in the cybersecurity community, offering a systematic way to create descriptions of malware families based on textual or binary patterns. These descriptions, known as rules, allow researchers to automate the detection and categorization of malicious files, streamlining the process of malware analysis and threat hunting
The Concept
YARA ia a rule-based approach. Each YARA rule consists of a set of strings and a boolean expression that defines the logic for detection. These strings can be simple text, hexadecimal byte patterns, or even regular expressions. The boolean expression, known as the condition, determines how the presence of these strings in a file leads to a match.
For example, a basic YARA rule might specify that if any of three defined patterns are found in a file, that file should be flagged as suspicious. This allows researchers to craft both simple and complex rules, adapting to the malware development evolving door.
A typical YARA rule includes metadata, strings to search for, and a condition. Consider the following 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