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YARA · CAPE Sandbox (CAPEv2)

CAPE_Stealcv2Strings

StealcV2 string decryption

GenericCAPE Sandbox (CAPEv2)GNU General Public License v3.0Compiles with YARA-X
Author
kevoreilly
Date
2023-02-22
Modified
2025-09-01
Score / Quality
75 / 70

What this rule detects

StealcV2 string decryption

Targets: Windows PE.

It defines 4 patterns (0 text, 4 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
stealcv2strings.yarGNU General Public License v3.0
rule CAPE_Stealcv2Strings : FILE
{
	meta:
		description = "StealcV2 string decryption"
		author = "kevoreilly"
		id = "d99fcc9c-35cc-5494-a0cd-738f3ae8d367"
		date = "2023-02-22"
		modified = "2025-09-01"
		reference = "https://github.com/kevoreilly/CAPEv2"
		source_url = "https://github.com/kevoreilly/CAPEv2/blob/6b15e76f28cd83fd1187da6c9aaaad2174255356/analyzer/windows/data/yara/Stealc.yar#L28-L43"
		license_url = "https://github.com/kevoreilly/CAPEv2/blob/6b15e76f28cd83fd1187da6c9aaaad2174255356/LICENSE"
		logic_hash = "923f70edb3ad70957576994008729bf7a087479eed1973c42161aa96fa694baa"
		score = 75
		quality = 70
		tags = "FILE"
		cape_options = "bp0=$decode32*,action0=string:[esp],bp1=$decode64,action1=string:eax,bp2=$dump,action2=dumpstrings,count=0,typestring=Stealc Strings"
		packed = "2f42dcf05dd87e6352491ff9d4ea3dc3f854df53d548a8da0c323be42df797b6"
		packed = "8301936f439f43579cffe98e11e3224051e2fb890ffe9df680bbbd8db0729387"

	strings:
		$decode32 = {AB AB AB AB 8B 45 0C 89 4E 10 89 4E 14 39 45 08 75 0B C7 46 14 0F 00 00 00 88 0E EB 0F 2B 45 08 50 51 FF 75 ?? 8B}
		$decode64 = {40 53 48 83 EC 20 48 8B 19 48 85 DB 74 ?? 48 8B 53 18 48 83 FA 0F 76 2C 48 8B 0B 48 FF C2 48 81 FA 00 10 00 00 72}
		$dump32 = {33 C0 89 46 30 88 46 34 89 46 38 89 46 3C 89 46 40 89 46 44 89 46 48 89 46 4C 89 46 50 89 46 54 89 46 58 8B C6 5F 5E C3}
		$dump64 = {48 8B C7 89 6F 40 40 88 6F 44 48 89 6F 48 48 89 6F 50 48 89 6F 58 48 89 6F 60 48 89 6F 68 48 89 6F 70 48 89 6F 78 48 89}

	condition:
		uint16( 0 ) == 0x5A4D and 2 of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$decode32hex{AB AB AB AB 8B 45 0C 89 4E 10 89 4E 14 39 45 08 75 0B C7 46 14 0F 00 00 00 88 0E EB 0F 2B 45 08 50 51 FF 75 ?? 8B}
$decode64hex{40 53 48 83 EC 20 48 8B 19 48 85 DB 74 ?? 48 8B 53 18 48 83 FA 0F 76 2C 48 8B 0B 48 FF C2 48 81 FA 00 10 00 00 72}
$dump32hex{33 C0 89 46 30 88 46 34 89 46 38 89 46 3C 89 46 40 89 46 44 89 46 48 89 46 4C 89 46 50 89 46 54 89 46 58 8B C6 5F 5E C3}
$dump64hex{48 8B C7 89 6F 40 40 88 6F 44 48 89 6F 48 48 89 6F 50 48 89 6F 58 48 89 6F 60 48 89 6F 68 48 89 6F 70 48 89 6F 78 48 89}

Condition

uint16( 0 ) == 0x5A4D and 2 of them

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • At least 2 patterns in the rule must match.

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References

Licence & attribution

Author: kevoreilly

Source repository: CAPE Sandbox (CAPEv2) @ 6b15e76f28

Licence: GNU General Public License v3.0 (repository licence)

Copyright notice: Cuckoo Sandbox is copyrighted by the Cuckoo Foundation.

Original rule

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

Rule id: d99fcc9c-35cc-5494-a0cd-738f3ae8d367

Metadata

cape_optionsbp0=$decode32*,action0=string:[esp],bp1=$decode64,action1=string:eax,bp2=$dump,action2=dumpstrings,count=0,typestring=Stealc Strings
packed2f42dcf05dd87e6352491ff9d4ea3dc3f854df53d548a8da0c323be42df797b6
packed8301936f439f43579cffe98e11e3224051e2fb890ffe9df680bbbd8db0729387

Tags:FILE

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