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EMBEERESEARCH_Win_Solarmarker_Bytecodes

Detects bytecodes present in solarmarker Packer

Suspicious / huntingSolarmarkerEmbee ResearchDetection Rule License 1.1Compiles with YARA-X
Author
Matthew @ Embee_Research
Date
2023-09-10
Modified
2023-09-11
Score / Quality
75 / 75

What this rule detects

Detects bytecodes present in solarmarker Packer

Associated malware family: Solarmarker.

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-solarmarker-bytecodes.yarDetection Rule License 1.1
import "dotnet"

rule EMBEERESEARCH_Win_Solarmarker_Bytecodes : FILE
{
	meta:
		description = "Detects bytecodes present in solarmarker Packer"
		author = "Matthew @ Embee_Research"
		id = "d405e7ae-f09b-5993-a510-e5e1bc289898"
		date = "2023-09-10"
		modified = "2023-09-11"
		reference = "https://github.com/embee-research/Yara-detection-rules/"
		source_url = "https://github.com/embee-research/Yara-detection-rules//blob/ac56d6f6fd2a30c8cb6e5c0455d6519210a8b0f4/Rules/win_solarmarker_bytecodes_aug_2023.yar#L3-L21"
		license_url = "N/A"
		hash = "a433dad1e31f2e19ab5d22b6348c73fa4c874502acc20d5517d785b554754279"
		logic_hash = "52256184706b7173ee8e8683ac79c1b9d4773778c135e4dae255376c0a6651fb"
		score = 75
		quality = 75
		tags = "FILE"

	strings:
		$s1 = {8C ?? ?? ?? ?? 28 ?? ?? ?? ?? 0A 20 ?? ?? ?? ?? 13 ?? 06 11 ?? 20 ?? ?? ?? ?? 58 D1 8C ?? ?? ?? ?? 28 ?? ?? ?? ?? 0A 20 ?? ?? ?? ?? 13 ?? 06 11 ?? 20 ?? ?? ?? ?? 58 D1 8C ?? ?? ?? ?? 28 ?? ?? ?? ??}

	condition:
		dotnet.is_dotnet and filesize < 7000KB and $s1
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$s1hex{8C ?? ?? ?? ?? 28 ?? ?? ?? ?? 0A 20 ?? ?? ?? ?? 13 ?? 06 11 ?? 20 ?? ?? ?? ?? 58 D1 8C ?? ?? ?? ?? 28 ?? ?? ?? ?? 0A 20 ?? ?? ?? ?? 13 ?? 06 11 ?? 20 ?? ?? ?? …

Condition

dotnet.is_dotnet and filesize < 7000KB and $s1

In plain words (Heuristic)

  • The file must be smaller than 7000KB (a cheap guard that skips large files).
  • 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).

  • a433dad1e31f2e19ab5d22b6348c73fa4c874502acc20d5517d785b554754279

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: d405e7ae-f09b-5993-a510-e5e1bc289898

Tags:FILE

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