Windows Event Log Access Tampering Via Registry

Status: experimental
Severity: high
Log source: product windows, category registry_set
Author: X__Junior
Source: github.com/SigmaHQ/sigma

Detects changes to the Windows EventLog channel permission values. It focuses on changes to the Security Descriptor Definition Language (SDDL) string, as modifications to these values can restrict access to specific users or groups, potentially aiding in defense evasion by controlling who can view or modify a event log channel. Upon execution, the user shouldn't be able to access the event log channel via the event viewer or via utilities such as "Get-EventLog" or "wevtutil".

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1112` Modify Registry, `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
Defense Impairment	`T1112` Modify Registry

Event coverage

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

Rule body yaml

title: Windows Event Log Access Tampering Via Registry
id: ba226dcf-d390-4642-b9af-b534872f1156
status: experimental
description: |
    Detects changes to the Windows EventLog channel permission values. It focuses on changes to the Security Descriptor Definition Language (SDDL) string, as modifications to these values can restrict access to specific users or groups, potentially aiding in defense evasion by controlling who can view or modify a event log channel. Upon execution, the user shouldn't be able to access the event log channel via the event viewer or via utilities such as "Get-EventLog" or "wevtutil".
references:
    - https://www.atomicredteam.io/atomic-red-team/atomics/T1562.002#atomic-test-8---modify-event-log-channel-access-permissions-via-registry---powershell
    - https://www.youtube.com/watch?v=uSYvHUVU8xY
    - https://learn.microsoft.com/en-us/windows/win32/secauthz/security-descriptor-definition-language
author: X__Junior
date: 2025-01-16
modified: 2025-08-16
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.defense-impairment
    - attack.t1547.001
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    # O:SYG:SYD:(D;;0x1;;;WD)
    # O:BAG:SYD:(A;;0x2;;;S-1-15-2-1)(D;;0x1;;;WD)
    selection_key_1:
        TargetObject|contains: '\SYSTEM\CurrentControlSet\Services\EventLog\'
        TargetObject|endswith: '\CustomSD'
    selection_key_2:
        TargetObject|contains:
            - '\Policies\Microsoft\Windows\EventLog\'
            - '\Microsoft\Windows\CurrentVersion\WINEVT\Channels'
        TargetObject|endswith: '\ChannelAccess'
    selection_details:
        - Details|contains: 'D:(D;'
        - Details|contains|all:
              - 'D:('
              - ')(D;'
    filter_main_trustedinstaller:
        Image: 'C:\Windows\servicing\TrustedInstaller.exe'
    filter_main_tiworker:
        Image|startswith: 'C:\Windows\WinSxS\'
        Image|endswith: '\TiWorker.exe'
    filter_optional_empty:
        Image: ''
    filter_optional_null:
        Image: null
    condition: 1 of selection_key_* and selection_details and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Administrative activity, still unlikely
level: high

Stages and Predicates

Stage 0: `condition`

1 of selection_key_* and selection_details and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection_key_1`

selection_key_1:
    TargetObject|contains: '\SYSTEM\CurrentControlSet\Services\EventLog\'
    TargetObject|endswith: '\CustomSD'

Stage 2: `selection_key_2`

selection_key_2:
    TargetObject|contains:
        - '\Policies\Microsoft\Windows\EventLog\'
        - '\Microsoft\Windows\CurrentVersion\WINEVT\Channels'
    TargetObject|endswith: '\ChannelAccess'

Stage 3: `selection_details`

selection_details:
    - Details|contains: 'D:(D;'
    - Details|contains|all:
          - 'D:('
          - ')(D;'

Stage 4: `not filter_main_*`

filter_main_trustedinstaller:
    Image: 'C:\Windows\servicing\TrustedInstaller.exe'
filter_main_tiworker:
    Image|startswith: 'C:\Windows\WinSxS\'
    Image|endswith: '\TiWorker.exe'

Stage 5: `not filter_optional_*`

filter_optional_empty:
    Image: ''
filter_optional_null:
    Image: null

Exclusions

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

Field	Kind	Excluded values
`Image`	ends_with	`\TiWorker.exe`
`Image`	starts_with	`C:\Windows\WinSxS\`
`Image`	eq	`C:\Windows\servicing\TrustedInstaller.exe`
`Image`	is_null	(no value, null check)

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
`Details`	match	`)(D;` `D:(` `D:(D;`
`TargetObject`	ends_with	`\ChannelAccess` corpus 2 (sigma 2) `\CustomSD`
`TargetObject`	match	`\Microsoft\Windows\CurrentVersion\WINEVT\Channels` `\Policies\Microsoft\Windows\EventLog\` `\SYSTEM\CurrentControlSet\Services\EventLog\` 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)

Windows Event Log Access Tampering Via Registry

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_key_1`

Stage 2: `selection_key_2`

Stage 3: `selection_details`

Stage 4: `not filter_main_*`

Stage 5: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Windows Event Log Access Tampering Via Registry

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_key_1

Stage 2: selection_key_2

Stage 3: selection_details

Stage 4: not filter_main_*

Stage 5: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_key_1`

Stage 2: `selection_key_2`

Stage 3: `selection_details`

Stage 4: `not filter_main_*`

Stage 5: `not filter_optional_*`