Elastic Defend high stable eql

Regsvr32 with Unusual Arguments

Identifies unusual instances of Regsvr32 with suspicious keywords or paths in the process command line value. Adversaries may abuse regsvr32.exe to proxy execution of malicious code.

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Detection Logic

process where event.action == "start" and process.name : "regsvr32.exe" and
 (
  (process.args_count == 2 and process.working_directory : "?:\\" and not process.working_directory : "C:\\") or
  process.command_line :
          ("*.jpg*",
           "*.png*",
           "*.gif*",
           "*.bmp*",
           "*.jpeg*",
           "*.TIFF*",
           "*.tmp*",
           "*.dat*",
           "*.pdf*",
           "*.doc*",
           "*.xls*",
           "*.ppt*",
           "*.txt*",
           "* ?:/*/*",
           "* ..\\*",
           "*DumpStack.log*",
           "*:\\Users\\Public\\*",
           "*:\\Users\\*\\Documents\\*",
           "*:\\Users\\*\\Pictures\\*",
           "*:\\Users\\*\\Music\\*",
           "*:\\Users\\*\\Pictures\\*",
           "*:\\Windows\\Tasks\\*",
           "*:\\Windows\\System32\\tasks\\*",
           "*\\DavWWWRoot\\*")
  ) and

 not process.args : ("?:\\Program Files (x86)\\*", "?:\\Program Files\\*") and

 /*  path traversal */
 not (process.command_line : "* ..\\*" and process.command_line :"* ..\\*\\*") and
 not process.parent.executable : "?:\\Program Files (x86)\\Tencent\\QQPCMgr\\*\\QQPCTray.exe" and
 not process.command_line :
             ("*\\Program Files (x86)\\Tencent\\QQPCMgr\\*.dat*",
              "*QQPCMgr*TSWebMon64.dat*",
              "*BarTender Suite\\Codejock.DockingPane.x64.v15.3.1.ocx*") and
 not process.parent.executable : "?:\\Eaglesoft\\Shared Files\\OcxReg.exe" and
 not process.args : ("?:\\windows\\system32\\ChartFX.ClientServer.Data.dll", "?:\\Windows\\SysWOW64\\ChartFX.ClientServer.Data.dll") and
 not (process.args : "?:\\Users\\*\\AppData\\Local\\Microsoft\\TeamsMeetingAddin\\*\\Microsoft.Teams.AddinLoader.dll" and process.args : "/i:user") and
 not (process.args : "..\\*.dll" and process.working_directory : "?:\\Program Files\\LANDesk\\ManagementSuite\\Install Only Files\\") and
 not (process.args : "..\\*.dll" and
      descendant of
       [process where event.action == "start" and
        process.executable : ("?:\\Program Files\\LANDesk\\ManagementSuite\\Install Only Files\\LaunchApp.exe",
                              "?:\\Program Files (x86)\\LANDesk\\ManagementSuite\\Install Only Files\\LaunchApp.exe")]) and
 not (process.parent.name : "msiexec.exe" and process.parent.args : "-Embedding") and
 not process.parent.executable : "C:\\Program Files\\LANDesk\\ManagementSuite\\Install Only Files\\LaunchApp.exe" and
 not (process.executable : "?:\\Users\\*\\AppData\\Local\\Temp\\SSM*.tmp\\REGSVR32.EXE" and process.args : "?:\\WINDOWS\\system32\\*.dll") and
 not process.args : ("?:\\Windows\\Microsoft.NET\\*",
                     "?:\\Windows\\assembly\\NativeImages*",
                     "?:\\Windows\\Installer\\MSI*",
                     "?:\\Windows\\system32\\Codejock.DockingPane.*.ocx",
                     "?:\\windows\\system32\\Msjet35.dll",
                     "?:\\windows\\system32\\Msrd2x35.dll",
                     "System.Data.dll", "Atalasoft.*.dll", "DTI.ImageMan.Codecs.Pdf.dll") and
 not (process.name : "regsvr32.exe" and process.parent.executable : "C:\\Windows\\SysWOW64\\cmd.exe" and
      process.args : ("C:\\Users\\*\\AppData\\Local\\Temp\\is-*.tmp\\QClickV?\\Driver\\QClickV?_x64.ocx",
                      "(x86)\\eClinicalWorks_Prod\\RegBlg.bat")) and
 process.command_line != "regsvr32  DevExpress.Data.v14.1.dll"

Field Validations

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