APT_MAL_NK_3CX_Malicious_Samples_Mar23_4_RID3504

YARA detection rule by MalGamy (Nextron Systems) · CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/

Detects decrypted payload loaded inside 3CXDesktopApp.exe which downloads info stealer

rule APT_MAL_NK_3CX_Malicious_Samples_Mar23_4_RID3504 : APT DEMO MAL NK {
   meta:
      description = "Detects decrypted payload loaded inside 3CXDesktopApp.exe which downloads info stealer"
      author = "MalGamy (Nextron Systems)"
      reference = "https://twitter.com/WhichbufferArda/status/1641404343323688964?s=20"
      date = "2023-03-29 15:55:11"
      score = 80
      customer = "demo"
      license = "CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/"
      
      tags = "APT, DEMO, MAL, NK"
      minimum_yara = "3.5.0"
      
   strings:
      $op1 = { 41 69 D0 [4] 8B C8 C1 E9 ?? 33 C1 8B C8 C1 E1 ?? 81 C2 [4] 33 C1 43 8D 0C 02 02 C8 49 C1 EA ?? 41 88 0B 8B C8 C1 E1 ?? 33 C1 44 69 C2 [4] 8B C8 C1 E9 ?? 33 C1 8B C8 C1 E1 ?? 41 81 C0 [4] 33 C1 4C 0F AF CF 4D 03 CA 45 8B D1 4C 0F AF D7 41 8D 0C 11 49 C1 E9 ?? 02 C8 } 
      $op2 = { 4D 0F AF CC 44 69 C2 [4] 4C 03 C9 45 8B D1 4D 0F AF D4 41 8D 0C 11 41 81 C0 [4] 02 C8 49 C1 E9 ?? 41 88 4B ?? 4D 03 D1 8B C8 45 8B CA C1 E1 ?? 33 C1 } 
      $op3 = { 33 C1 4C 0F AF C7 8B C8 C1 E1 ?? 4D 03 C2 33 C1 } 
   condition: 
      2 of them
}

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

399ca215-0ac1-4706-8f01-d9548216c596

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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