XOR_4byte_Key_RID2BD9

YARA detection rule by Florian Roth · CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/

Detects an executable encrypted with a 4 byte XOR (also used for Derusbi Trojan)

rule XOR_4byte_Key_RID2BD9 : APT DEMO EXE FILE {
   meta:
      description = "Detects an executable encrypted with a 4 byte XOR (also used for Derusbi Trojan)"
      author = "Florian Roth"
      reference = "http://blog.airbuscybersecurity.com/post/2015/11/Newcomers-in-the-Derusbi-family"
      date = "2015-12-15 09:24:01"
      score = 60
      customer = "demo"
      license = "CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/"
      
      tags = "APT, DEMO, EXE, FILE"
      minimum_yara = "3.5.0"
      
   strings:
      $s1 = { 85 C9 74 0A 31 06 01 1E 83 C6 04 49 EB F2 } 
   condition: 
      uint16 ( 0 ) == 0x5a4d and filesize < 900KB and all of them
}

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

23927d3f-4f47-458a-aefb-2b36f911e701

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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

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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.

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

[[ currentRule.title ]]

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