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EMBEERESEARCH_Win_Njrat_Bytecodes_Oct_2023

MalwareNjratEmbee ResearchDetection Rule License 1.1Compiles with YARA-X
Author
Matthew @ Embee_Research
Date
2023-10-03
Score / Quality
75 / 75

What this rule detects

Associated malware family: Njrat.

Targets: .NET assembly.

It defines 1 patterns (0 text, 1 hex, 0 regex). YARA modules used: dotnet.

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

Includes the imports needed to compile it on its own.

win-njrat-bytecodes-oct-2023.yarDetection Rule License 1.1
import "dotnet"

rule EMBEERESEARCH_Win_Njrat_Bytecodes_Oct_2023
{
	meta:
		description = ""
		author = "Matthew @ Embee_Research"
		id = "9e39587a-e878-5f99-806f-e9964952f0ac"
		date = "2023-10-03"
		modified = "2023-10-03"
		reference = "https://github.com/embee-research/Yara-detection-rules/"
		source_url = "https://github.com/embee-research/Yara-detection-rules//blob/ac56d6f6fd2a30c8cb6e5c0455d6519210a8b0f4/Rules/win_njrat_bytecodes_oct_2023.yar#L3-L22"
		license_url = "N/A"
		hash = "59d6e2958780d15131c102a93fefce6e388e81da7dc78d9c230aeb6cab7e3474"
		hash = "4c56ade4409add1d78eac3b202a9fbd6afbd71878c31f798026082467ace2628"
		hash = "d5a78790a1b388145424327e78f019584466d30d2d450bba832c0128aa3cd274"
		logic_hash = "7df39219e2f2da55e461b1536e92ab125d488a048e41daaaa1fb9516be395d10"
		score = 75
		quality = 75
		tags = ""

	strings:
		$s1 = {14 80 ?? ?? ?? ?? 16 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 14 80 ?? ?? ?? ?? 73 ?? ?? ?? ?? 80 ?? ?? ?? ?? 20 ?? ?? ?? ?? 8D ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 14 80 ?? ?? ?? ?? 2A }

	condition:
		dotnet.is_dotnet and $s1
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$s1hex{14 80 ?? ?? ?? ?? 16 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 14 80 ?? ?? ?? ?? 73 ?? ?? ?? ?? 80 ?? ?? ?? ?? 20 ?? ?? ?? ?? 8D ?? ?? ?? ?? 80 ?? ?? ?? ?? …

Condition

dotnet.is_dotnet and $s1

In plain words (Heuristic)

  • Uses the dotnet module.
  • Pattern $s1 must be present.

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References

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

  • 59d6e2958780d15131c102a93fefce6e388e81da7dc78d9c230aeb6cab7e3474
  • 4c56ade4409add1d78eac3b202a9fbd6afbd71878c31f798026082467ace2628
  • d5a78790a1b388145424327e78f019584466d30d2d450bba832c0128aa3cd274

Licence & attribution

Author: Matthew @ Embee_Research

Source repository: Embee Research @ ac56d6f6fd

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 9e39587a-e878-5f99-806f-e9964952f0ac

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