MAL_Chrysalis_Backdoor_Feb26

rule MAL_Chrysalis_Backdoor_Feb26 {
   meta:
      description = "Detects Chrysalis backdoor, seen being used in the compromise of the infrastructure hosting Notepad++ by Chinese APT group Lotus Blossom"
      author = "X__Junior"
      date = "2026-02-02"
      reference = "https://www.rapid7.com/blog/post/tr-chrysalis-backdoor-dive-into-lotus-blossoms-toolkit/"
      hash = "e2e3d78437cf9d48c2b2264e44bb36bc2235834fc45bbb50b5d6867f336711e3"
      score = 80
      id = "c3621431-9e20-5497-ad0a-e371063e7656"
   strings:
      $opa1 = { 8B 4D ?? C1 CF ?? C1 C1 ?? 03 F9 D1 C3 8B 4D ?? C1 C1 ?? 03 F9 03 FB 8B 5D ?? 69 CF ?? ?? ?? ?? BF ?? ?? ?? ?? 2B F9 EB }
      $opa2 = { F7 E9 [0-1] 8B C2 C1 E8 ?? 03 C2 8D 0C 40 8A C3 34 ?? [0-2] 0F B6 [1-4] 0F B6 C3 8B 5D [1-3] 0F 45 D0 }

      $opb1 = { 0F B6 84 35 ?? ?? ?? ?? 88 84 3D ?? ?? ?? ?? 88 8C 35 ?? ?? ?? ?? 0F B6 84 3D ?? ?? ?? ?? 8B 8D ?? ?? ?? ?? 03 C2 0F B6 C0 0F B6 84 05 ?? ?? ?? ?? 30 04 19 43 3B 9D ?? ?? ?? ?? 7C }
   condition:
      (1 of ($opa*) and $opb1)
      or
      all of ($opa*)
}