REVERSINGLABS_Win32_Infostealer_Stealc

YARA detection rule by ReversingLabs · GPL-2.0

Yara rule that detects StealC infostealer.

rule REVERSINGLABS_Win32_Infostealer_Stealc: TC_DETECTION MALICIOUS MALWARE FILE {
  meta:
    description         = "Yara rule that detects StealC infostealer."
    author              = "ReversingLabs"
    id                  = "b53bbf15-3e94-513c-91a9-83dda421063b"
    date                = "2023-06-07"
    modified            = "2023-06-07"
    reference           = "ReversingLabs"
    source_url          = "https://github.com/reversinglabs/reversinglabs-yara-rules//blob/d35a6845dcd00f2840f690611612b04dda6d195d/yara/infostealer/Win32.Infostealer.StealC.yara#L1-L57"
    license_url         = "https://github.com/reversinglabs/reversinglabs-yara-rules//blob/d35a6845dcd00f2840f690611612b04dda6d195d/LICENSE"
    logic_hash          = "bea1cf370150387eb185deff726e10e660e7eb571c20d22878def08b36f457bf"
    score               = 75
    quality             = 90
    tags                = "TC_DETECTION, MALICIOUS, MALWARE, FILE"
    status              = "RELEASED"
    sharing             = "TLP:WHITE"
    category            = "MALWARE"
    tc_detection_type   = "Infostealer"
    tc_detection_name   = "StealC"
    tc_detection_factor = 5
    importance          = 25

  strings:
    $resolve_windows_api           = {
      55 8B EC 51 83 65 ?? ?? 56 64 A1 ?? ?? ?? ?? 8B 40 ?? 8B 40 ?? 8B 00 8B 00 8B 40 ??
      89 45 ?? 8B 75 ?? 89 35 ?? ?? ?? ?? 85 F6 0F 84 ?? ?? ?? ?? E8 ?? ?? ?? ?? FF 35 ??
      ?? ?? ?? A3 ?? ?? ?? ?? 56 FF D0 FF 35 ?? ?? ?? ?? A3 ?? ?? ?? ?? FF 35
    }
    $load_sqlite3_functions        = {
      55 8B EC 83 EC ?? 6A ?? FF 15 ?? ?? ?? ?? 8B 4D ?? 50 89 45 ?? 89 4D ?? 8B 4D ?? 8D
      45 ?? 50 89 4D ?? E8 ?? ?? ?? ?? 83 C4 ?? 85 C0 74 ?? 8D 45 ?? 57 89 45 ?? 8B 7D ??
      B9 ?? ?? ?? ?? 33 C0 F3 AA 5F 33 C0 C9 C3 8B 45 ?? 85 C0 74 ?? 53 8B 58 ?? 56 8B 70
      ?? FF 35 ?? ?? ?? ?? 8B C6 E8 ?? ?? ?? ?? FF 35 ?? ?? ?? ?? A3 ?? ?? ?? ?? 8B C6 E8
      ?? ?? ?? ?? FF 35 ?? ?? ?? ?? A3 ?? ?? ?? ?? 8B C6 E8 ?? ?? ?? ?? FF 35 ?? ?? ?? ??
      A3 ?? ?? ?? ?? 8B C6 E8 ?? ?? ?? ?? FF 35 ?? ?? ?? ?? A3 ?? ?? ?? ?? 8B C6 E8 ?? ??
      ?? ?? FF 35 ?? ?? ?? ?? A3 ?? ?? ?? ?? 8B C6 E8 ?? ?? ?? ?? FF 35 ?? ?? ?? ?? A3
    }
    $check_license_expiration_date = {
      55 8B EC 83 E4 ?? 83 EC ?? 57 33 C0 66 89 44 24 ?? 83 64 24 ?? ?? 8D 7C 24 ?? AB AB
      AB 66 AB 33 C0 66 89 44 24 ?? 8D 7C 24 ?? AB AB AB 66 AB 33 C0 21 44 24 ?? 8D 7C 24
      ?? AB 8D 7C 24 ?? AB 8D 44 24 ?? 50 FF 15 ?? ?? ?? ?? 8D 7C 24 ?? E8 ?? ?? ?? ?? 8D
      4C 24 ?? 51 8D 4C 24 ?? 51 8D 4C 24 ?? 51 FF 35 ?? ?? ?? ?? FF 30 FF 15 ?? ?? ?? ??
      8B 44 24 ?? 83 C4 ?? E8 ?? ?? ?? ?? 8D 44 24 ?? 50 8D 44 24 ?? 50 FF 15 ?? ?? ?? ??
      8D 44 24 ?? 50 8D 44 24 ?? 50 FF 15 ?? ?? ?? ?? 8B 44 24 ?? 3B 44 24 ?? 72 ?? 77 ??
      8B 44 24 ?? 3B 44 24 ?? 76 ?? 6A ?? FF 15 ?? ?? ?? ?? 5F 8B E5 5D C3
    }

  condition:
    uint16(0) == 0x5A4D and ($resolve_windows_api) and ($load_sqlite3_functions) and ($check_license_expiration_date)
}

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

da074e38-94a7-4405-92e0-f7a831d9421f

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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 ]]

What do these messages mean?

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

[[ currentRule.title ]]

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