MAL_Netfilter_May_2021_1

YARA detection rule by Arkbird_SOLG

Detect Netfilter rootkit

rule MAL_Netfilter_May_2021_1 {
   meta:
        description = "Detect Netfilter rootkit"
        author = "Arkbird_SOLG"
        reference = "https://twitter.com/struppigel/status/1405483373280235520"
        date = "2021-06-18"
        hash1 = "63d61549030fcf46ff1dc138122580b4364f0fe99e6b068bc6a3d6903656aff0"
        hash2 = "8249e9c0ac0840a36d9a5b9ff3e217198a2f533159acd4bf3d9b0132cc079870"
        hash3 = "d64f906376f21677d0585e93dae8b36248f94be7091b01fd1d4381916a326afe"
        tlp = "White"
        adversary = "Chinese APT Group"
   strings:
        $seq1 = { 48 8b 05 a9 57 ff ff 45 33 c9 49 b8 32 a2 df 2d 99 2b 00 00 48 85 c0 74 05 49 3b c0 75 38 0f 31 48 c1 e2 20 48 8d 0d 85 57 ff ff 48 0b c2 48 33 c1 48 89 05 78 57 ff ff 66 44 89 0d 76 57 ff ff 48 8b 05 69 57 ff ff 48 85 c0 75 0a 49 8b c0 48 89 05 5a 57 ff ff 48 f7 d0 48 89 05 58 57 }
        $seq2 = { 48 83 ec 38 48 83 64 24 20 00 48 8d 05 83 4c 00 00 48 8d 15 24 d1 00 00 48 89 44 24 28 48 8d 4c 24 20 e8 4d 05 00 00 85 c0 78 16 4c 8d 05 22 d1 00 00 83 ca ff 48 8d 0d 00 d1 00 00 e8 39 05 00 00 48 83 c4 }
        $seq3 = { 45 33 c0 48 8d 4c 24 40 41 8d 50 01 ff 15 5d 62 00 00 c6 84 24 88 00 00 00 01 48 8d 84 24 88 00 00 00 48 89 46 18 48 8d 0d e2 fe ff ff 48 89 9e c0 00 00 00 48 8d 44 24 40 48 89 46 50 48 8d 44 24 30 48 89 46 48 65 48 8b 04 25 88 01 00 00 48 89 86 98 00 00 00 48 8b 86 b8 00 00 00 40 88 7e 40 c6 40 b8 06 4c 89 78 e0 48 89 58 e8 c7 40 c0 01 00 00 00 c7 40 c8 0d 00 00 00 48 89 58 d0 48 8b 86 b8 00 00 00 48 89 48 f0 48 8d 4c 24 40 48 89 48 f8 c6 40 bb e0 48 8b 43 28 48 85 c0 74 2f 48 8b 48 10 48 85 c9 74 07 48 21 78 10 4c 8b f1 48 8b 08 48 85 c9 74 06 48 21 38 48 8b e9 48 8b 48 08 48 85 c9 74 08 48 83 60 08 00 48 8b f9 48 8b d6 49 8b cf ff 15 74 61 00 00 3d 03 01 00 00 75 19 48 83 64 24 20 00 48 8d 4c 24 40 41 b1 01 45 33 c0 33 d2 ff 15 64 61 00 00 48 8b 43 28 48 85 c0 74 1a 4d }
        $seq4 = { 8b 84 24 80 00 00 00 48 8d 54 24 38 48 8b 4c 24 30 44 8b ce 89 44 24 28 45 33 c0 48 89 7c 24 20 ff 15 66 2e 00 00 48 8b 4c 24 30 8b d8 ff 15 49 2e 00 00 48 8b 4c 24 30 ff 15 26 2d 00 00 8b }
        $s1 = "%sc=%s" fullword ascii
        $s2 = { 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 25 30 32 78 }
        $s3 = "NETIO.SYS" fullword ascii
   condition:
        uint16(0) == 0x5a4d and filesize > 20KB and (3 of ($seq*) or 2 of ($s*))
}

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

daa3b286-4bfe-4983-bd81-33e864fb1824

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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 ]]

What does this mean?

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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