Try in Splunk Security Cloud

Description

The following analytic identifies the Windows Windows Remote Auto Dialer, rasautou.exe executing an arbitrary DLL. This technique is used to execute arbitrary shellcode or DLLs via the rasautou.exe LOLBin capability. During triage, review parent and child process behavior including file and image loads.

  • Type: TTP
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Processes
  • Last Updated: 2022-02-15
  • Author: Michael Haag, Splunk
  • ID: 6f42b8ce-1e15-11ec-ad5a-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1055.001 Dynamic-link Library Injection Defense Evasion, Privilege Escalation
T1218 System Binary Proxy Execution Defense Evasion
T1055 Process Injection Defense Evasion, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
  • PR.PT
  • DE.CM
CIS20
  • CIS 8
CVE
1
2
3
4
5
6
7
8
| from read_ssa_enriched_events() 
| where "Endpoint_Processes" IN(_datamodels) 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=ucast(map_get(input_event, "process"), "string", null), process_name=ucast(map_get(input_event, "process_name"), "string", null), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where cmd_line IS NOT NULL AND process_name IS NOT NULL AND process_name="rasautou.exe" AND (like (cmd_line, "%-d %") AND like (cmd_line, "%-p %")) 
| eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)) 
| eval body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

:information_source: windows_rasautou_dll_execution_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • dest_device_id
  • process_name
  • parent_process_name
  • process_path
  • dest_user_id
  • process
  • cmd_line

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives will be limited to applications that require Rasautou.exe to load a DLL from disk. Filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ attempting to load a DLL in a suspicious manner.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 1