Rundll32.exe as Parent Process (Sysmon)

Group by: _time, host
Source: github.com/anvilogic-forge/armory

Adversaries may abuse rundll32.exe to proxy execution of malicious code. Using rundll32.exe, may avoid triggering security tools that may not monitor execution of the rundll32.exe process because of allowlists or false positives from normal operations. Rundll32.exe is commonly associated with executing DLL payloads

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218.011` System Binary Proxy Execution: Rundll32

References

https://redcanary.com/threat-detection-report/techniques/rundll32/

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

id: '5850.18101'
title: Rundll32.exe as Parent Process
description: 'Adversaries may abuse rundll32.exe to proxy execution of malicious code.
  Using rundll32.exe, may avoid triggering security tools that may not monitor execution
  of the rundll32.exe process because of allowlists or false positives from normal
  operations. Rundll32.exe is commonly associated with executing DLL payloads. Threat
  Actor Association: MuddyWater, TA505, Wizard Spider - Software Association: Bazar,
  Clop, Conti, Quantum, Rhysida, Trickbot'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` ("EventCode=1" OR "<EventID>1<")
  TERM(rundll32) | regex parent_process_name="(?i)(rundll32)" | table _time, host,
  user parent_*, process, process_*, signature_id | 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/

Stages and Predicates

Stage 1: `search`

`get_endpoint_data` `get_endpoint_data_sysmon` ("EventCode=1" OR "<EventID>1<") TERM(rundll32)

Stage 2: `regex`

| regex parent_process_name="(?i)(rundll32)"

Stage 3: `table`

| table _time, host, user parent_*, process, process_*, signature_id

Stage 4: `bucket`

| bin span=1s

Stage 5: `stats`

| stats values(*) as * by _time, host

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`parent_process_name`	regex_match	`"(?i)(rundll32)"` corpus 2 (splunk 2)	`field:"parent_process_name" kind:regex_match`

Search terms

These SPL tokens match against raw event text.

Stage	Term
1	`"EventCode=1"`
1	`"<EventID>1<"`
1	`rundll32`