Suspicious Volume Shadow Copy Vssapi.dll Load

Status: test
Severity: high
Log source: product windows, category image_load
Author: frack113
Source: github.com/SigmaHQ/sigma

Detects the image load of VSS DLL by uncommon executables

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1490` Inhibit System Recovery

Event coverage

Provider	Event	Title
Sysmon	Event ID 7	Image loaded

Rule body yaml

title: Suspicious Volume Shadow Copy Vssapi.dll Load
id: 37774c23-25a1-4adb-bb6d-8bb9fd59c0f8
related:
    - id: 333cdbe8-27bb-4246-bf82-b41a0dca4b70 # vss_ps.dll
      type: similar
    - id: 48bfd177-7cf2-412b-ad77-baf923489e82 # vsstrace.dll
      type: similar
status: test
description: Detects the image load of VSS DLL by uncommon executables
references:
    - https://github.com/ORCx41/DeleteShadowCopies
author: frack113
date: 2022-10-31
modified: 2026-05-18
tags:
    - attack.impact
    - attack.t1490
logsource:
    category: image_load
    product: windows
detection:
    selection:
        ImageLoaded|endswith: '\vssapi.dll'
    filter_main_windows:
        - Image:
              - 'C:\Windows\explorer.exe'
              - 'C:\Windows\ImmersiveControlPanel\SystemSettings.exe'
        - Image|startswith:
              - 'C:\Windows\System32\'
              - 'C:\Windows\SysWOW64\'
              - 'C:\Windows\Temp\{' # Installers
              - 'C:\Windows\WinSxS\'
              - 'C:\$WinREAgent\Scratch\'
    filter_main_program_files:
        # When using this rule in your environment replace the "Program Files" folder by the exact applications you know use this. Examples would be software such as backup solutions
        Image|startswith:
            - 'C:\Program Files\'
            - 'C:\Program Files (x86)\'
    filter_main_null_image:
        Image: null
    filter_optional_programdata_packagecache:
        # The following filter is required because of many FPs cause by:
        #   C:\ProgramData\Package Cache\{10c6cfdc-27af-43fe-bbd3-bd20aae88451}\dotnet-sdk-3.1.425-win-x64.exe
        #   C:\ProgramData\Package Cache\{b9cfa33e-ace4-49f4-8bb4-82ded940990a}\windowsdesktop-runtime-6.0.11-win-x86.exe
        #   C:\ProgramData\Package Cache\{50264ff2-ad47-4569-abc4-1c350f285fb9}\aspnetcore-runtime-6.0.11-win-x86.exe
        #   C:\ProgramData\Package Cache\{2dcef8c3-1563-4149-a6ec-5b6c98500d7d}\dotnet-sdk-6.0.306-win-x64.exe
        #   etc.
        Image|startswith: 'C:\ProgramData\Package Cache\'
    filter_optional_avira:
        Image|contains|all:
            - '\temp\is-'
            - '\avira_system_speedup.tmp'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    ImageLoaded|endswith: '\vssapi.dll'

Stage 2: `not filter_main_*`

filter_main_windows:
    - Image:
          - 'C:\Windows\explorer.exe'
          - 'C:\Windows\ImmersiveControlPanel\SystemSettings.exe'
    - Image|startswith:
          - 'C:\Windows\System32\'
          - 'C:\Windows\SysWOW64\'
          - 'C:\Windows\Temp\{'
          - 'C:\Windows\WinSxS\'
          - 'C:\$WinREAgent\Scratch\'
filter_main_program_files:
    Image|startswith:
        - 'C:\Program Files\'
        - 'C:\Program Files (x86)\'
filter_main_null_image:
    Image: null

Stage 3: `not filter_optional_*`

filter_optional_programdata_packagecache:
    Image|startswith: 'C:\ProgramData\Package Cache\'
filter_optional_avira:
    Image|contains|all:
        - '\temp\is-'
        - '\avira_system_speedup.tmp'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`Image`	eq	`C:\Windows\ImmersiveControlPanel\SystemSettings.exe`
`Image`	eq	`C:\Windows\explorer.exe`
`Image`	is_null	(no value, null check)
`Image`	starts_with	`C:\$WinREAgent\Scratch\`
`Image`	starts_with	`C:\Program Files (x86)\`
`Image`	starts_with	`C:\Program Files\`
`Image`	starts_with	`C:\Windows\SysWOW64\`
`Image`	starts_with	`C:\Windows\System32\`
`Image`	starts_with	`C:\Windows\Temp\{`
`Image`	starts_with	`C:\Windows\WinSxS\`
`Image`	match	`\avira_system_speedup.tmp`
`Image`	match	`\temp\is-`
`Image`	starts_with	`C:\ProgramData\Package Cache\`

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
`ImageLoaded`	ends_with	`\vssapi.dll` corpus 2 (sigma 2)

`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)

Suspicious Volume Shadow Copy Vssapi.dll Load

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Suspicious Volume Shadow Copy Vssapi.dll Load

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_*

Stage 3: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_optional_*`