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Description

The following analytic detects suspicious raw access reads to the device disk partition of a host machine. It leverages Sysmon EventCode 9 logs to identify processes attempting to read or write to the boot sector, excluding legitimate system processes. This activity is significant as it is commonly associated with destructive actions by adversaries, such as wiping, encrypting, or overwriting the boot sector, as seen in attacks involving malware like HermeticWiper. If confirmed malicious, this behavior could lead to severe impacts, including system inoperability, data loss, or compromised boot integrity.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-28
  • Author: Teoderick Contreras, Splunk
  • ID: a85aa37e-9647-11ec-90c5-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1561.002 Disk Structure Wipe Impact
T1561 Disk Wipe Impact
Kill Chain Phase
  • Actions On Objectives
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`sysmon` EventCode=9 Device = \\Device\\HarddiskVolume* NOT (Image IN("*\\Windows\\System32\\*", "*\\Windows\\SysWOW64\\*")) 
| stats count min(_time) as firstTime max(_time) as lastTime by dest signature signature_id process_guid process_name process_path Device 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_raw_access_to_disk_volume_partition_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_raw_access_to_disk_volume_partition_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
  • signature
  • signature_id
  • process_guid
  • process_name
  • process_path
  • Device
  • EventCode
  • Image

How To Implement

To successfully implement this search, you need to be ingesting logs with the raw access read event (like sysmon eventcode 9), process name and process guid from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

This event is really notable but we found minimal number of normal application from system32 folder like svchost.exe accessing it too. In this case we used 'system32' and 'syswow64' path as a filter for this detection.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
90.0 90 100 Process accessing disk partition $Device$ in $dest$

: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: 2