Allow Service Access Using Security Descriptor Tampering Via Sc.EXE

Status: test
Severity: high
Log source: product windows, category process_creation
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects suspicious DACL modifications to allow access to a service from a suspicious trustee. This can be used to override access restrictions set by previous ACLs.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1543.003` Create or Modify System Process: Windows Service
Privilege Escalation	`T1543.003` Create or Modify System Process: Windows Service

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Allow Service Access Using Security Descriptor Tampering Via Sc.EXE
id: 6c8fbee5-dee8-49bc-851d-c3142d02aa47
related:
    - id: a537cfc3-4297-4789-92b5-345bfd845ad0 # Generic SD tampering
      type: similar
status: test
description: Detects suspicious DACL modifications to allow access to a service from a suspicious trustee. This can be used to override access restrictions set by previous ACLs.
references:
    - https://twitter.com/0gtweet/status/1628720819537936386
    - https://itconnect.uw.edu/tools-services-support/it-systems-infrastructure/msinf/other-help/understanding-sddl-syntax/
    - https://learn.microsoft.com/en-us/windows/win32/secauthz/sid-strings
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-28
modified: 2025-10-22
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1543.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_sc:
        - Image|endswith: '\sc.exe'
        - OriginalFileName: 'sc.exe'
    selection_sdset:
        CommandLine|contains|all:
            - 'sdset'
            - 'A;' # Allow Access
    selection_trustee:
        CommandLine|contains:
            - ';IU' # Interactively logged-on user
            - ';SU' # Service logon user
            - ';BA' # Built-in administrators
            - ';SY' # Local system
            - ';WD' # Everyone
    filter_optional_hexnode:
        ParentImage: 'C:\Hexnode\Hexnode Agent\Current\HexnodeAgent.exe'
    condition: all of selection_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_* and not 1 of filter_optional_*

Stage 1: `selection_sc`

selection_sc:
    - Image|endswith: '\sc.exe'
    - OriginalFileName: 'sc.exe'

Stage 2: `selection_sdset`

selection_sdset:
    CommandLine|contains|all:
        - 'sdset'
        - 'A;'

Stage 3: `selection_trustee`

selection_trustee:
    CommandLine|contains:
        - ';IU'
        - ';SU'
        - ';BA'
        - ';SY'
        - ';WD'

Stage 4: `not filter_optional_hexnode`

filter_optional_hexnode:
    ParentImage: 'C:\Hexnode\Hexnode Agent\Current\HexnodeAgent.exe'

Exclusions

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

Field	Kind	Excluded values
`ParentImage`	eq	`C:\Hexnode\Hexnode Agent\Current\HexnodeAgent.exe`

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
`CommandLine`	match	`;BA` corpus 2 (sigma 2) `;IU` corpus 2 (sigma 2) `;SU` corpus 2 (sigma 2) `;SY` corpus 2 (sigma 2) `;WD` corpus 2 (sigma 2) `A;` `sdset` corpus 5 (sigma 5)
`Image`	ends_with	`\sc.exe` corpus 30 (sigma 30)
`OriginalFileName`	eq	`sc.exe` corpus 26 (sigma 12, splunk 10, elastic 4)

`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)

Allow Service Access Using Security Descriptor Tampering Via Sc.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_sc`

Stage 2: `selection_sdset`

Stage 3: `selection_trustee`

Stage 4: `not filter_optional_hexnode`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Allow Service Access Using Security Descriptor Tampering Via Sc.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_sc

Stage 2: selection_sdset

Stage 3: selection_trustee

Stage 4: not filter_optional_hexnode

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_sc`

Stage 2: `selection_sdset`

Stage 3: `selection_trustee`

Stage 4: `not filter_optional_hexnode`