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Rhadamanthys Yara Rule Update #2737

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Rhadamanthys Yara Rule Update #2737

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4 changes: 3 additions & 1 deletion data/yara/CAPE/Rhadamanthys.yar
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Original file line number Diff line number Diff line change
@@ -1,13 +1,15 @@
rule Rhadamanthys
{
meta:
author = "kevoreilly"
author = "kevoreilly, YungBinary"
description = "Rhadamanthys Loader"
cape_type = "Rhadamanthys Loader"
strings:
$rc4 = {88 4C 01 08 41 81 F9 00 01 00 00 7C F3 89 75 08 33 FF 8B 4D 08 3B 4D 10 72 04 83 65 08 00}
$code = {8B 4D FC 3B CF 8B C1 74 0D 83 78 04 02 74 1C 8B 40 1C 3B C7 75 F3 3B CF 8B C1 74 57 83 78 04 17 74 09 8B 40 1C 3B C7 75 F3 EB}
$conf = {46 BB FF 00 00 00 23 F3 0F B6 44 31 08 03 F8 23 FB 0F B6 5C 39 08 88 5C 31 08 88 44 39 08 02 C3 8B 5D 08 0F B6 C0 8A 44 08 08}
$beef = { 57 8D 44 33 FC 53 83 C6 FC 50 56 E8 ?? ?? ?? ?? 83 C4 10 66 81 3F EF BE 0F 85 E6 02 00 00 }
$config_2 = { 0F B6 4F 2A 8D 77 2A 33 C0 6A 03 89 ?? ?? 89 ?? ?? 89 ?? ?? 8B C1 }
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medium

The new string $config_2 seems a bit generic due to the repeated use of 89 ?? ??. This pattern corresponds to a 3-byte mov instruction like mov [reg+disp8], reg, where both the registers and the displacement are wildcards. With 6 wildcard bytes out of 19 total, this string might be prone to false positives, especially with a 2 of them condition.

Could this be made more specific by filling in some of the ?? bytes if the registers or displacements are constant across samples? A more specific signature would improve the reliability of the detection.

$cape_string = "cape_options"
condition:
2 of them and not $cape_string
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