Detection rules › Splunk

Windows Raw Access To Disk Volume Partition

Status
production
Severity
low
Group by
Device, dest, dvc, process_guid, process_id, process_name, signature, signature_id, user_id, vendor_product
Author
Teoderick Contreras, Splunk
Source
github.com/splunk/security_content

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.

Known false positives

  • There are som minimal number of normal applications from system32 folder like svchost.exe accessing the MBR. In this case we used 'system32' and 'syswow64' path as a filter for this detection.

MITRE ATT&CK coverage

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 9: RawAccessRead

Rule body

name: Windows Raw Access To Disk Volume Partition
id: a85aa37e-9647-11ec-90c5-acde48001122
version: 13
creation_date: '2022-02-25'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
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.
data_source:
    - Sysmon EventID 9
search: '`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 dvc process_exec process_guid process_id process_name process_path signature signature_id user_id vendor_product Device Image | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_raw_access_to_disk_volume_partition_filter`'
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: There are som minimal number of normal applications from system32 folder like svchost.exe accessing the MBR. In this case we used 'system32' and 'syswow64' path as a filter for this detection.
references:
    - https://blog.talosintelligence.com/2022/02/threat-advisory-hermeticwiper.html
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Process accessing disk partition $Device$ on $dest$
analytic_story:
    - CISA AA22-264A
    - Graceful Wipe Out Attack
    - Data Destruction
    - Hermetic Wiper
    - Caddy Wiper
    - BlackByte Ransomware
    - NjRAT
    - Disk Wiper
    - PathWiper
    - Void Manticore
asset_type: Endpoint
mitre_attack_id:
    - T1561.002
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint

Stages and Predicates

Stage 1: search

`sysmon` EventCode=9 Device = \\Device\\HarddiskVolume* NOT (Image IN("*\\Windows\\System32\\*", "*\\Windows\\SysWOW64\\*"))

Stage 2: stats

| stats count min(_time) as firstTime max(_time) as lastTime by dest dvc process_exec process_guid process_id process_name process_path signature signature_id user_id vendor_product Device Image

Stage 3: search

| `security_content_ctime(firstTime)`

Stage 4: search

| `security_content_ctime(lastTime)`

Stage 5: search

| `windows_raw_access_to_disk_volume_partition_filter`

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Imagein"*\\Windows\\SysWOW64\\*", "*\\Windows\\System32\\*"excludes:Image

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Deviceeq
  • \\Device\\HarddiskVolume*
field:"Device" kind:eq value:"\\Device\\HarddiskVolume*"
EventCodeeq
  • 9 corpus 2 (splunk 2)
field:"EventID" kind:eq value:"9"