Elastic Defend high stable eql

Unusual File Written or Modified in Startup Folder

Identifies suspicious file extensions or names written to the startup folder. Adversaries may use this technique to maintain persistence.

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Detection Logic

file where event.action != "deletion" and
  process.pid != 4 and process.executable != null and
  file.name != null and not user.id : ("S-1-5-18", "S-1-5-19", "S-1-5-20") and
  file.path : ("?:\\Users\\*\\AppData\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\*",
               "?:\\ProgramData\\Microsoft\\Windows\\Start Menu\\Programs\\StartUp\\*") and
  (
   /* file extensions rarely written to Startup folder by legit installers */
   file.extension : ("exe", "com", "scr", "dll", "hta", "ps1", "cmd", "url", "wsh", "wsf", "vbe", "jse", "sick", "png", "jpg", "manifest", "ahk", "jar") or

   /* suspicious file names */
   length(file.name) <= 6 or
   file.name :
        ("*Microsoft*",
         "*fuck*",
         "*:*",
         "*.*.",
         "*update*",
         "*windows*",
         "*setup*",
         "*googl*",
         "*adobe*",
         "*chrome*")
   ) and
   not process.executable :
               ("?:\\Windows\\SysWOW64\\msiexec.exe",
                "?:\\Windows\\system32\\msiexec.exe",
                "?:\\Windows\\explorer.exe",
                "?:\\Windows\\System32\\svchost.exe",
                "?:\\Windows\\System32\\dllhost.exe",
                "?:\\Windows\\System32\\xcopy.exe",
                "?:\\ProgramData\\Microsoft\\Windows Defender\\Platform\\*.exe",
                "?:\\ProgramData\\Microsoft\\Windows Defender Advanced Threat Protection\\Platform\\*.exe",
                "?:\\Program Files\\Windows Defender Advanced Threat Protection\\*.exe",
                "\\Device\\Mup\\*\\SysVol\\*") and
    not (process.executable : ("?:\\Program Files\\*.exe", "?:\\Program Files (x86)\\*.exe") and not process.name : "javaw.exe") and
    not (process.name : "cmd.exe" and file.extension : "cmd") and
    not (process.code_signature.subject_name :
                 ("Intercontinental Exchange, Inc.", "Chocolatey Software, Inc.", "ONELAUNCH TECHNOLOGIES INC.", 
                  "Notepad++", "Ghisler Software GmbH", "Western Union Holdings Inc.", "AnyDesk Software GmbH", "Learnpulse SAS") and
         process.code_signature.status : ("trusted", "errorExpired", "errorCode_endpoint*")) and
    not (process.executable : "?:\\Windows\\System32\\notepad.exe" and file.extension : ("bat", "cmd")) and
    not (process.executable : "C:\\Windows\\SysWOW64\\cscript.exe" and file.name : "WUPOSStartup.exe") and
    not (process.name : "cmd.exe" and file.name : "MonitorES.exe")

Field Validations

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