Classes Autorun Keys Modification

Status: test
Severity: medium
Log source: product windows, category registry_set
Author: Victor Sergeev, Daniil Yugoslavskiy, Gleb Sukhodolskiy, Timur Zinniatullin, oscd.community, Tim Shelton, frack113 (split)
Source: github.com/SigmaHQ/sigma

Detects modification of Windows Registry Classes keys used for persistence. Adversaries modify these autostart extensibility points (ASEP) to execute malicious code when file types are opened or actions are performed. Various legitimate software also uses these keys. Currently, this rule only filters out known legitimate software paths, thus it is recommended to review and tune filters for your environment to reduce false positives before deploying to production.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1547.001` Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder
Privilege Escalation	`T1547.001` Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Event coverage

Provider	Event	Title
Sysmon	Event ID 13	RegistryEvent (Value Set)

Rule body yaml

title: Classes Autorun Keys Modification
id: 9df5f547-c86a-433e-b533-f2794357e242
related:
    - id: 17f878b8-9968-4578-b814-c4217fc5768c
      type: obsolete
status: test
description: |
    Detects modification of Windows Registry Classes keys used for persistence.
    Adversaries modify these autostart extensibility points (ASEP) to execute malicious code when file types are opened or actions are performed.
    Various legitimate software also uses these keys. Currently, this rule only filters out known legitimate software paths,
    thus it is recommended to review and tune filters for your environment to reduce false positives before deploying to production.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1547.001/T1547.001.md
    - https://learn.microsoft.com/en-us/sysinternals/downloads/autoruns
    - https://gist.github.com/GlebSukhodolskiy/0fc5fa5f482903064b448890db1eaf9d # a list with registry keys
author: Victor Sergeev, Daniil Yugoslavskiy, Gleb Sukhodolskiy, Timur Zinniatullin, oscd.community, Tim Shelton, frack113 (split)
date: 2019-10-25
modified: 2025-10-22
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1547.001
logsource:
    category: registry_set
    product: windows
detection:
    selection_classes_base:
        TargetObject|contains: '\Software\Classes'
    selection_classes_target:
        TargetObject|contains:
            - '\Folder\ShellEx\ExtShellFolderViews'
            - '\Folder\ShellEx\DragDropHandlers'
            - '\Folder\Shellex\ColumnHandlers'
            - '\Filter'
            - '\Exefile\Shell\Open\Command\(Default)'
            - '\Directory\Shellex\DragDropHandlers'
            - '\Directory\Shellex\CopyHookHandlers'
            - '\CLSID\{AC757296-3522-4E11-9862-C17BE5A1767E}\Instance'
            - '\CLSID\{ABE3B9A4-257D-4B97-BD1A-294AF496222E}\Instance'
            - '\CLSID\{7ED96837-96F0-4812-B211-F13C24117ED3}\Instance'
            - '\CLSID\{083863F1-70DE-11d0-BD40-00A0C911CE86}\Instance'
            - '\Classes\AllFileSystemObjects\ShellEx\DragDropHandlers'
            - '\.exe'
            - '\.cmd'
            - '\ShellEx\PropertySheetHandlers'
            - '\ShellEx\ContextMenuHandlers'
    filter_main_drivers:
        Image: 'C:\Windows\System32\drvinst.exe'
    filter_main_empty:
        Details: '(Empty)'
    filter_main_null:
        Details: null
    filter_main_svchost:
        Image: 'C:\Windows\System32\svchost.exe'
        # If more targets are found from "svchost". Please exclude the whole image
        TargetObject|contains: '\lnkfile\shellex\ContextMenuHandlers\'
    filter_optional_msoffice:
        Details: '{807583E5-5146-11D5-A672-00B0D022E945}'
    condition: all of selection_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Legitimate software automatically (mostly, during installation) sets up autorun keys for legitimate reason
    - Legitimate administrator sets up autorun keys for legitimate reason
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_* and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection_classes_base`

selection_classes_base:
    TargetObject|contains: '\Software\Classes'

Stage 2: `selection_classes_target`

selection_classes_target:
    TargetObject|contains:
        - '\Folder\ShellEx\ExtShellFolderViews'
        - '\Folder\ShellEx\DragDropHandlers'
        - '\Folder\Shellex\ColumnHandlers'
        - '\Filter'
        - '\Exefile\Shell\Open\Command\(Default)'
        - '\Directory\Shellex\DragDropHandlers'
        - '\Directory\Shellex\CopyHookHandlers'
        - '\CLSID\{AC757296-3522-4E11-9862-C17BE5A1767E}\Instance'
        - '\CLSID\{ABE3B9A4-257D-4B97-BD1A-294AF496222E}\Instance'
        - '\CLSID\{7ED96837-96F0-4812-B211-F13C24117ED3}\Instance'
        - '\CLSID\{083863F1-70DE-11d0-BD40-00A0C911CE86}\Instance'
        - '\Classes\AllFileSystemObjects\ShellEx\DragDropHandlers'
        - '\.exe'
        - '\.cmd'
        - '\ShellEx\PropertySheetHandlers'
        - '\ShellEx\ContextMenuHandlers'

Stage 3: `not filter_main_*`

filter_main_drivers:
    Image: 'C:\Windows\System32\drvinst.exe'
filter_main_empty:
    Details: '(Empty)'
filter_main_null:
    Details: null
filter_main_svchost:
    Image: 'C:\Windows\System32\svchost.exe'
    TargetObject|contains: '\lnkfile\shellex\ContextMenuHandlers\'

Stage 4: `not filter_optional_msoffice`

filter_optional_msoffice:
    Details: '{807583E5-5146-11D5-A672-00B0D022E945}'

Exclusions

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

Field	Kind	Excluded values
`Image`	eq	`C:\Windows\System32\svchost.exe`
`TargetObject`	match	`\lnkfile\shellex\ContextMenuHandlers\`
`Details`	eq	`(Empty)`
`Details`	is_null	(no value, null check)
`Image`	eq	`C:\Windows\System32\drvinst.exe`
`Details`	eq	`{807583E5-5146-11D5-A672-00B0D022E945}`

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
`TargetObject`	match	`\.cmd` `\.exe` `\CLSID\{083863F1-70DE-11d0-BD40-00A0C911CE86}\Instance` corpus 2 (sigma 2) `\CLSID\{7ED96837-96F0-4812-B211-F13C24117ED3}\Instance` corpus 2 (sigma 2) `\CLSID\{ABE3B9A4-257D-4B97-BD1A-294AF496222E}\Instance` corpus 2 (sigma 2) `\CLSID\{AC757296-3522-4E11-9862-C17BE5A1767E}\Instance` corpus 2 (sigma 2) `\Classes\AllFileSystemObjects\ShellEx\DragDropHandlers` `\Directory\Shellex\CopyHookHandlers` corpus 2 (sigma 2) `\Directory\Shellex\DragDropHandlers` corpus 2 (sigma 2) `\Exefile\Shell\Open\Command\(Default)` `\Filter` `\Folder\ShellEx\DragDropHandlers` corpus 2 (sigma 2) `\Folder\ShellEx\ExtShellFolderViews` corpus 2 (sigma 2) `\Folder\Shellex\ColumnHandlers` corpus 2 (sigma 2) `\ShellEx\ContextMenuHandlers` corpus 2 (sigma 2) `\ShellEx\PropertySheetHandlers` corpus 2 (sigma 2) `\Software\Classes`

`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)

Classes Autorun Keys Modification

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_classes_base`

Stage 2: `selection_classes_target`

Stage 3: `not filter_main_*`

Stage 4: `not filter_optional_msoffice`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Classes Autorun Keys Modification

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_classes_base

Stage 2: selection_classes_target

Stage 3: not filter_main_*

Stage 4: not filter_optional_msoffice

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_classes_base`

Stage 2: `selection_classes_target`

Stage 3: `not filter_main_*`

Stage 4: `not filter_optional_msoffice`