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Description

This search is to detect a suspicious bcdedit commandline to configure the host to boot in safe mode with network config. This technique was seen in blackMatter ransomware where it force the compromised host to boot in safe mode to continue its encryption and bring back to normal boot using bcdedit deletevalue command. This TTP can be a good alert for host that booted from safe mode forcefully since it need to modify the boot configuration to bring it back to normal.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-09-06
  • Author: Teoderick Contreras, Splunk
  • ID: 81f1dce0-0f18-11ec-a5d7-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1490 Inhibit System Recovery Impact
Kill Chain Phase
  • Exploitation
NIST
CIS20
CVE
1
2
3
4
5
6
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name = bcdedit.exe Processes.process="*/set*" Processes.process="*{current}*"  Processes.process="*safeboot*" Processes.process="*network*" by Processes.process_name Processes.process Processes.parent_process_name Processes.dest Processes.user 
|`drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `change_to_safe_mode_with_network_config_filter`

Macros

The SPL above uses the following Macros:

:information_source: change_to_safe_mode_with_network_config_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
  • Processes.process_name
  • Processes.process
  • Processes.parent_process_name
  • Processes.parent_process
  • Processes.dest
  • Processes.user

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where renamed rundll32.exe may be used.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 bcdedit process with commandline $process$ to force safemode boot the $dest$

: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