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EMBEERESEARCH_Win_Xworm_Simple_Strings

Detects simple strings present in unobfuscated xworm

Suspicious / huntingEmbee ResearchDetection Rule License 1.1Compiles with YARA-X
Author
Matthew @ Embee_Research
Date
2023-08-30
Modified
2023-10-18
Score / Quality
75 / 75

What this rule detects

Detects simple strings present in unobfuscated xworm

Targets: .NET assembly.

It defines 4 patterns (4 text, 0 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-xworm-simple-strings.yarDetection Rule License 1.1
import "dotnet"

rule EMBEERESEARCH_Win_Xworm_Simple_Strings
{
	meta:
		description = "Detects simple strings present in unobfuscated xworm"
		author = "Matthew @ Embee_Research"
		id = "8d5d8f07-72fa-596b-a3fc-1dee4b7fd058"
		date = "2023-08-30"
		modified = "2023-10-18"
		reference = "https://github.com/embee-research/Yara-detection-rules/"
		source_url = "https://github.com/embee-research/Yara-detection-rules//blob/ac56d6f6fd2a30c8cb6e5c0455d6519210a8b0f4/Rules/win_xworm_simple_strings_sep_2023.yar#L3-L29"
		license_url = "N/A"
		hash = "4459d95c0493d640ecc9453cf6a4f2b7538b1a7b95032f70803fc726b8e40422"
		hash = "820bb1a31f421b90ea51efc3e71cc720c8c2784fb1e882e732e8fafb8631a389"
		logic_hash = "f7df310b24b2078249cdb670ece71ebe30f985c92b3e44b6dcf0e37405a26bc3"
		score = 75
		quality = 75
		tags = ""

	strings:
		$x1 = "XWorm V" wide nocase
		$s1 = "/create /f /RL HIGHEST /sc minute /mo 1 /tn " wide
		$s2 = "/create /f /sc minute /mo 1 /tn " wide
		$s3 = "-ExecutionPolicy Bypass Add-MpPreference -ExclusionPath " wide

	condition:
		dotnet.is_dotnet and $x1 and ( 2 of ( $s* ) )
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$x1text"XWorm V"wide nocase
$s1text"/create /f /RL HIGHEST /sc minute /mo 1 /tn "wide
$s2text"/create /f /sc minute /mo 1 /tn "wide
$s3text"-ExecutionPolicy Bypass Add-MpPreference -ExclusionPath "wide

Condition

dotnet.is_dotnet and $x1 and ( 2 of ( $s* ) )

In plain words (Heuristic)

  • At least 2 patterns in ( $s* ) must match.
  • Uses the dotnet module.
  • Pattern $x1 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).

  • 4459d95c0493d640ecc9453cf6a4f2b7538b1a7b95032f70803fc726b8e40422
  • 820bb1a31f421b90ea51efc3e71cc720c8c2784fb1e882e732e8fafb8631a389

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: 8d5d8f07-72fa-596b-a3fc-1dee4b7fd058

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