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fix NitrogenLoader YARA #3003

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Merged
kevoreilly merged 2 commits into from
May 18, 2026
Merged

fix NitrogenLoader YARA #3003

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4b849e1
fix NitrogenLoader YARA
ruppde May 4, 2026
6379581
Reorder condition in NitrogenLoader.yar
ruppde May 4, 2026
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3 changes: 2 additions & 1 deletion data/yara/CAPE/NitrogenLoader.yar
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Original file line number Diff line number Diff line change
Expand Up @@ -31,5 +31,6 @@ rule NitrogenLoader
$rc4decrypt_1 = {48 89 ?? 4? 89 ?? E8 [4] 4? 8B ?? 24 [1-4] 4? 89 ?? 4? 89 ?? 4? 89 C1 [0-1] 89 ?? E8 [4] 4? 89}
$rc4decrypt_2 = {E8 [4] 8B ?? 24 [1-4] 4? 89 ?? 48 89 ?? 4? 89 C1 E8 [3] FF}
condition:
(2 of ($string*) and any of ($syscall*)) or 4 of ($decrypt*) or ((3 of ($taskman_*) or 3 of ($installers*)) and all of ($rc4decrypt_*))
((2 of ($string*) and any of ($syscall*)) or 4 of ($decrypt*) or ((3 of ($taskman_*) or 3 of ($installers*)) and all of ($rc4decrypt_*)))
and uint16(0) == 0x5a4d
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@gemini-code-assist gemini-code-assist Bot May 4, 2026

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medium

For better performance, it is recommended to place the file header check (uint16(0) == 0x5a4d) at the beginning of the condition. This allows YARA to short-circuit the evaluation for non-PE files immediately, avoiding unnecessary processing of the more complex string and pattern matching logic.

        uint16(0) == 0x5a4d and
        ((2 of ($string*) and any of ($syscall*)) or 4 of ($decrypt*) or ((3 of ($taskman_*) or 3 of ($installers*)) and all of ($rc4decrypt_*)))

}