behavior/rules/windows/defense_evasion_rundll32_with_unusual_arguments.toml

[rule]
description = """
Identifies unusual instances of RunDLL32 with suspicious keywords or paths in the process command line value.
Adversaries may abuse rundll32.exe to proxy execution of malicious code.
"""
id = "cfaf983e-1129-464c-b0aa-270f42e20d3d"
license = "Elastic License v2"
name = "RunDLL32 with Unusual Arguments"
os_list = ["windows"]
reference = [
    "https://www.elastic.co/security-labs/dipping-into-danger",
    "https://www.elastic.co/security-labs/unmasking-financial-services-intrusion-ref0657",
    "https://www.elastic.co/security-labs/thawing-the-permafrost-of-icedid-summary",
]
version = "1.0.43"

query = '''
process where event.action == "start" and process.name : "rundll32.exe" and
  (
   /* suspicious extensions and paths */

   (process.command_line : "*\\AppData\\Local\\Temp\\*,*" and not process.command_line : "*.dll*") or
    process.command_line :
          ("*.jpg*,*",
           "*.png*,*",
           "*.gif*,*",
           "*.bmp*,*",
           "*.jpeg*,*",
           "*.TIFF*,*",
           "*.tmp*,*",
           "*.dat*,*",
           "*.txt*,*",
           "* ?:/*/*",
           "* ..\\*",
           "*:\\Users\\Public\\*,*",
           "*:\\Users\\*\\Documents\\*,*",
           "*:\\Users\\*\\Pictures\\*,*",
           "*:\\Users\\*\\Music\\*,*",
           "*:\\Windows\\Tasks\\*,*",
           "*:\\Windows\\System32\\tasks\\*,*",
           "*:\\Documents and Settings\\*,*",
           "*\\@SSL\\DavWWWRoot\\*",

           /* Issue #371 */
           "*.bin,*",
           "*.log,*",
           "*.nki,*",
           "*\\M?-*.dll,_run@*",
           "*%TEMP%\\*.cpl*",
           "*\\Users\\*\\Downloads\\*.cpl*",
           "*\\appdata\\roaming\\microsoft\\templates\\*,*",
           
           /* DLL exec by ordinal */
           "* #*", "*,#*") or
    process.command_line like "*rUNdlL32.eXe*" or

    /* fake Control_RunDLL export */
    (process.command_line : "*Control_RunDLL*" and not process.command_line : "*shell32.dll*Control_RunDLL*") or

    /* delayed execution */
    (process.parent.name : "cmd.exe" and process.parent.args : ("timeout", "ping", "choice") and process.parent.args : ("/nobreak", "/n", "/t")) or

    /* execution from temp with suspicious parent process tree */
    (process.command_line : "*\\AppData\\Local\\Temp\\*" and process.parent.name : ("wscript.exe", "cscript.exe", "wmiprvse.exe")) or

    /* suspicious parent powershell args */
    (process.parent.name : "powershell.exe" and
     process.parent.args : ("-enc", "IEX", "*wp-content*", "*wp-admin*", "*wp-includes*", "*$*$*$*$*$*", "*^*^*^*^*^*^*^*^*^*", "*.replace*") and
     not (process.args : "UpdatePerUserSystemParameters" and process.args : "USER32.DLL"))
    )

   /* False Positives */
   and not

  process.command_line :
           ("*JOBID=*",
            "*davclnt.dll,DavSetCookie*",
            "*PhotoViewer*ImageView_Fu*",
            "*url.dll,FileProtocolHandler*",
            "*zzzzInvokeManagedCustomActionOutOfProc*",
            "*,DeferredDelete*",
            "*:\\WINDOWS\\system32\\spool\\*",
            "*:\\Program Files (x86)\\*",
            "*:\\Program Files\\*",
            /* Issue #282 - FP */
            "*cryptext*CryptExt*",
            "*dfshim.dll*ShOpenVerbShortcut*",
            "*\\Documents\\DocuShare\\*",

            /* Issue #371 */
            "*ndfapi.dll,NdfRunDllDiagnoseWithAnswerFile*",
            "*FirewallControlPanel.dll,ShowNotificationDialog*",
            "*--type=renderer*--log-file=*",
            "*--lang=*--log-file=*",
            
            "*shell32*OpenAs_RunDLL*",
            "*dfshim*ShOpenVerbExtension*",
            "*printui*PrintUIEntry*",
            "*mshtml*PrintHTML*",
            "*shell32*#44*",
            "*shell32.dll*ShellExec_RunDLL*#*",
            "*EDGEHTML*#*"
            ) and not
            
   (process.command_line : "*.tmp*" and
    process.parent.executable : ("?:\\Windows\\System32\\msiexec.exe", "?:\\Windows\\SysWOW64\\msiexec.exe") and
    process.parent.args : "-Embedding") and
  not process.args : "?:\\ProgramData\\Parallels\\RASLogs\\tmp*.tmp,StopMemshell" and
  not (process.args : "?:\\Users\\Public\\IBM\\ClientSolutions\\Start_Programs\\Windows_*\\acsnative.dll*" and
       process.parent.executable : "?:\\Users\\Public\\IBM\\ClientSolutions\\Start_Programs\\Windows_*\\acslaunch_*.exe") and
  not process.parent.executable :
              ("?:\\Program Files\\Common Files\\BullGuardInstall\\BullGuard*.exe",
               "?:\\Program Files (x86)\\Intuit\\QuickBooks 20??\\QBW??.EXE",
               "?:\\Program Files\\Intuit\\QuickBooks 2022\\QBW.EXE", 
               "C:\\Users\\Public (x86)\\Spectra\\temp\\smsx.exe") and
  not (user.name : "user" and process.args : "file.dll,#*") and
  not (process.name : "rundll32.exe" and process.args : "uxtheme.dll,#64" and process.args : "?:\\WINDOWS\\Resources\\Themes\\*") and 
  not process.parent.executable :
                         ("?:\\Program Files\\NVIDIA Corporation\\*.exe",
                          "?:\\Program Files (x86)\\Windows Media Components\\Encoder\\wmstypelib.exe",
                          "?:\\Program Files\\Adobe\\Acrobat DC\\Acrobat\\AdobeCollabSync.exe") and
  not (process.name : "rundll32.exe" and
       process.args : ("dfshim.dll,ShArpMaintain",
                       "?:\\WINDOWS\\SYSTEM32\\MSHTML.dll,#125",
                       "dfshim.dll,ShOpenVerbApplication",
                       "?:\\WINDOWS\\System32\\shimgvw.dll,ImageView_PrintTo",
                       "?:\\Windows\\System32\\DriverStore\\FileRepository\\*",
                       "?:\\Windows\\system32\\hotplug.dll,HotPlugSafeRemovalDriveNotification",
                       "c:\\EWDK??\\Program Files\\Microsoft Visual Studio\\*,#1",
                       "?:\\ProgramData\\FastTrack Software\\Admin By Request\\ShellHelper32.dll,#1", 
                       "?:\\ProgramData\\FastTrack Software\\Admin By Request\\ShellHelper64.dll,#1", 
                       "C:\\Users\\Public\\IBM\\ClientSolutions\\Start_Programs\\Windows_x86-64\\acsnative.dll,", 
                       "C:\\Windows\\TEMP\\*.tmp\\uninshlp.dll,DeleteExeAndDeleteSelf",
                       "?:\\Users\\*\\AppData\\Local\\Temp\\ns*.tmp\\BgInstallAssist.dll,RunDll_*",
                       "?:\\WINDOWS\\Installer\\MSI*.tmp*")) and
  not (process.name : "rundll32.exe" and
       process.args : "?:\\Users\\*\\AppData\\Local\\Temp\\ns*.tmp\\*" and
       process.parent.executable : "?:\\Users\\*\\AppData\\Local\\Temp\\ns*.tmp") and
  not (process.parent.executable : "?:\\Program Files*\\Splashtop\\Splashtop Remote\\Client for STB\\strwinclt.exe" and
       process.args : "?:\\ProgramData\\FastTrack Software\\Admin By Request\\ShellHelper64.dll,#1") and
  not (process.name : "rundll32.exe" and process.command_line :  "\"C:\\Windows\\System32\\rundll32.exe\" \"C:\\Users\\*\\AppData\\Local\\Temp\\GLF*.tmp\",RunDll32_KillDTG" and
       process.parent.name : "BelMonitor.exe") and
  not process.command_line : "rundll32.exe \"C:\\ProgramData\\FastTrack Software\\Admin By Request\\ShellHelper??.dll\",#1"
'''

min_endpoint_version = "7.15.0"
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0

[[optional_actions]]
action = "rollback"
field = "process.entity_id"
state = 0

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1218"
name = "System Binary Proxy Execution"
reference = "https://attack.mitre.org/techniques/T1218/"
[[threat.technique.subtechnique]]
id = "T1218.011"
name = "Rundll32"
reference = "https://attack.mitre.org/techniques/T1218/011/"



[threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"

[internal]
min_endpoint_version = "7.15.0"