✄𐘗
text code block:
✄𐘗/* Identifies the modification of RDP Shadow registry or
  the execution of processes indicative of active shadow RDP session */

any where host.os.type == "windows" and
(
  (event.category == "registry" and event.type == "change" and
    registry.value : "Shadow" and
    registry.path : (
      "*\\Software\\Policies\\Microsoft\\Windows NT\\Terminal Services\\Shadow"
    ) and
    registry.data.strings : ("1", "0x00000001", "2", "0x00000002", "3", "0x00000003", "4", "0x00000004")

  ) or
  (event.category == "process" and event.type == "start" and
     (process.name : ("RdpSaUacHelper.exe", "RdpSaProxy.exe") and process.parent.name : "svchost.exe") or
     (?process.pe.original_file_name : "mstsc.exe" and process.args : "/shadow:*")
  )
)