rundll32 with No DLL in Command Line (Sysmon)

id: '26999.49289'
title: rundll32 with No DLL in Command Line
description: rundll32.exe is a legitimate Windows utility used to run functions stored
  in Dynamic Link Libraries. Typical usage would involve specifying a DLL file and
  a function to execute. Because rundll32 is a trusted system utility with the ability
  to execute code, it is a high value target for abuse by threat actors. This use
  case detects executions of rundll32.exe without a .dll referenced in the command
  line. Benign false positives from Internet Explorer parent processes have been filtered
  out. Living Off the Land Binary and Scripts (LOLBAS) (LOLBIN)
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
  TERM(rundll32) OR "rundll32.exe" | where (match(process_name, "(?i)rundll32\.exe")
  and not match(process, "(?i)(^\"C:\x5cWindows\x5csystem32\x5crundll32\.exe\"$)|(\.dll)"))
  and (not match(parent_process_name, "(?i)iexplore\.exe") and not match(process,
  "(?i)InetCpl\.cpl\,ClearMyTracksByProcess")) | table _time, host, user, process,
  process_*, parent_process, parent_process_* | bin span=1s | stats values(*) as *
  by _time, host '
techniques:
- defense-evasion:system binary proxy execution:rundll32
technique_id:
- T1218.011
data_category:
- Windows Sysmon
references:
- https://redcanary.com/threat-detection-report/techniques/rundll32/