Windows System File on Disk

Status: production
Group by: CreationUtcTime, computer_name, event_action, file_access_time, file_acl, file_hash, file_modify_time, file_name, file_size, process_guid, process_id, target_filename, user, vendor_product
Author: Michael Haag, Splunk
Source: github.com/splunk/security_content

The following analytic detects the creation of new .sys files on disk. It leverages the Endpoint.Filesystem data model to identify and log instances where .sys files are written to the filesystem. This activity is significant because .sys files are often used as kernel mode drivers, and their unauthorized creation can indicate malicious activity such as rootkit installation. If confirmed malicious, this could allow an attacker to gain kernel-level access, leading to full system compromise, persistent control, and the ability to bypass security mechanisms.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1068` Exploitation for Privilege Escalation

Event coverage

Provider	Event	Title
Sysmon	Event ID 11	FileCreate

Rule body splunk

name: Windows System File on Disk
id: 993ce99d-9cdd-42c7-a2cf-733d5954e5a6
version: 9
creation_date: '2022-05-16'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: Hunting
description: The following analytic detects the creation of new .sys files on disk. It leverages the Endpoint.Filesystem data model to identify and log instances where .sys files are written to the filesystem. This activity is significant because .sys files are often used as kernel mode drivers, and their unauthorized creation can indicate malicious activity such as rootkit installation. If confirmed malicious, this could allow an attacker to gain kernel-level access, leading to full system compromise, persistent control, and the ability to bypass security mechanisms.
data_source:
    - Sysmon EventID 11
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem
      WHERE Filesystem.file_name="*.sys*"
      BY Filesystem.action Filesystem.dest Filesystem.file_access_time
         Filesystem.file_create_time Filesystem.file_hash Filesystem.file_modify_time
         Filesystem.file_name Filesystem.file_path Filesystem.file_acl
         Filesystem.file_size Filesystem.process_guid Filesystem.process_id
         Filesystem.user Filesystem.vendor_product
    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_system_file_on_disk_filter`
how_to_implement: To successfully implement this search you need to be ingesting information on files from your endpoints into the `Endpoint` datamodel in the `Filesystem` node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product. In addition, filtering may occur by adding NOT (Filesystem.file_path IN ("*\\Windows\\*", "*\\Program File*", "*\\systemroot\\*","%SystemRoot%*", "system32\*")). This will level out the noise generated to potentally lead to generating findings.
known_false_positives: False positives will be present. Filter as needed.
references:
    - https://redcanary.com/blog/tracking-driver-inventory-to-expose-rootkits/
analytic_story:
    - CISA AA22-264A
    - Windows Drivers
    - Crypto Stealer
asset_type: Endpoint
mitre_attack_id:
    - T1068
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1068/drivers/sysmon_sys_filemod.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

Stages and Predicates

Stage 1: `tstats`

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem
  WHERE Filesystem.file_name="*.sys*"
  BY Filesystem.action Filesystem.dest Filesystem.file_access_time
     Filesystem.file_create_time Filesystem.file_hash Filesystem.file_modify_time
     Filesystem.file_name Filesystem.file_path Filesystem.file_acl
     Filesystem.file_size Filesystem.process_guid Filesystem.process_id
     Filesystem.user Filesystem.vendor_product

Stage 2: `search`

| `drop_dm_object_name(Filesystem)`

Stage 3: `search`

| `security_content_ctime(firstTime)`

Stage 4: `search`

| `security_content_ctime(lastTime)`

Stage 5: `search`

| `windows_system_file_on_disk_filter`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`Filesystem.file_name`	eq	`".sys"`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Windows System File on Disk

MITRE ATT&CK coverage

Event coverage

Rule body splunk

Stages and Predicates

Stage 1: `tstats`

Stage 2: `search`

Stage 3: `search`

Stage 4: `search`

Stage 5: `search`

Indicators

Keyboard shortcuts

Search operators

Windows System File on Disk

MITRE ATT&CK coverage

Event coverage

Rule body splunk

Stages and Predicates

Stage 1: tstats

Stage 2: search

Stage 3: search

Stage 4: search

Stage 5: search

Indicators

Stage 1: `tstats`

Stage 2: `search`

Stage 3: `search`

Stage 4: `search`

Stage 5: `search`