APT_MAL_NK_3CX_Malicious_Samples_Mar23_3

YARA detection rule by Florian Roth , X__Junior (Nextron Systems) · NOASSERTION

Detects malicious DLLs related to 3CX compromise (decrypted payload)

rule APT_MAL_NK_3CX_Malicious_Samples_Mar23_3 {
   meta:
      description = "Detects malicious DLLs related to 3CX compromise (decrypted payload)"
      author = "Florian Roth , X__Junior (Nextron Systems)"
      reference = "https://www.reddit.com/r/crowdstrike/comments/125r3uu/20230329_situational_awareness_crowdstrike/"
      date = "2023-03-29"
      score = 80
      hash1 = "aa4e398b3bd8645016d8090ffc77d15f926a8e69258642191deb4e68688ff973"
      id = "d2d361b6-8485-57eb-b6eb-88785f42e93e"
    strings:
      $opa1 = { 41 81 C0 ?? ?? ?? ?? 02 C8 49 C1 E9 ?? 41 88 4B ?? 4D 03 D1 8B C8 45 8B CA C1 E1 ?? 33 C1 41 69 D0 ?? ?? ?? ?? 8B C8 C1 E9 ?? 33 C1 8B C8 C1 E1 ?? 81 C2 ?? ?? ?? ?? 33 C1 43 8D 0C 02 02 C8 49 C1 EA ?? 41 88 0B 8B C8 C1 E1 ?? 33 C1 44 69 C2 ?? ?? ?? ?? 8B C8 C1 E9 ?? 33 C1 8B C8 C1 E1 ?? 41 81 C0 } 
      $opa2 = { 8B C8 41 69 D1 ?? ?? ?? ?? C1 E1 ?? 33 C1 45 8B CA 8B C8 C1 E9 ?? 33 C1 81 C2 ?? ?? ?? ?? 8B C8 C1 E1 ?? 33 C1 41 8B C8 4C 0F AF CF 44 69 C2 ?? ?? ?? ?? 4C 03 C9 45 8B D1 4C 0F AF D7} 

      $opb1 = { 45 33 C9 48 89 6C 24 ?? 48 8D 44 24 ?? 48 89 6C 24 ?? 8B D3 48 89 B4 24 ?? ?? ?? ?? 48 89 44 24 ?? 45 8D 41 ?? FF 15 } 
      $opb2 = { 44 8B 0F 45 8B C6 48 8B 4D ?? 49 8B D7 44 89 64 24 ?? 48 89 7C 24 ?? 44 89 4C 24 ?? 4C 8D 4D ?? 48 89 44 24 ?? 44 89 64 24 ?? 4C 89 64 24 ?? FF 15} 
      $opb3 = { 48 FF C2 66 44 39 2C 56 75 ?? 4C 8D 4C 24 ?? 45 33 C0 48 8B CE FF 15 ?? ?? ?? ?? 85 C0 0F 84 ?? ?? ?? ?? 44 0F B7 44 24 ?? 33 F6 48 8B 54 24 ?? 45 33 C9 48 8B 0B 48 89 74 24 ?? 89 74 24 ?? C7 44 24 ?? ?? ?? ?? ?? 48 89 74 24 ?? FF 15 } 
      $opb4 = { 33 C0 48 8D 6B ?? 4C 8D 4C 24 ?? 89 44 24 ?? BA ?? ?? ?? ?? 48 89 44 24 ?? 48 8B CD 89 44 24 ?? 44 8D 40 ?? 8B F8 FF 15} 
    condition:
      ( all of ($opa*) )
      or
      ( 1 of ($opa*) and 1 of ($opb*) )
      or
      ( 3 of ($opb*) )
}

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

5e73d4d5-58e0-4152-a7e5-87b42f9f8f66

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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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