Shell Open Registry Keys Manipulation

Status: test
Severity: high
Log source: product windows, category registry_event
Author: Christian Burkard (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the shell open key manipulation (exefile and ms-settings) used for persistence and the pattern of UAC Bypass using fodhelper.exe, computerdefaults.exe, slui.exe via registry keys (e.g. UACMe 33 or 62)

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1546.001` Event Triggered Execution: Change Default File Association
Privilege Escalation	`T1546.001` Event Triggered Execution: Change Default File Association, `T1548.002` Abuse Elevation Control Mechanism: Bypass User Account Control

Event coverage

Provider	Event	Title
Sysmon	Event ID 12	RegistryEvent (Object create and delete)
Sysmon	Event ID 13	RegistryEvent (Value Set)
Sysmon	Event ID 14	RegistryEvent (Key and Value Rename)

Rule body yaml

title: Shell Open Registry Keys Manipulation
id: 152f3630-77c1-4284-bcc0-4cc68ab2f6e7
related:
    - id: dd3ee8cc-f751-41c9-ba53-5a32ed47e563
      type: similar
status: test
description: Detects the shell open key manipulation (exefile and ms-settings) used for persistence and the pattern of UAC Bypass using fodhelper.exe, computerdefaults.exe, slui.exe via registry keys (e.g. UACMe 33 or 62)
references:
    - https://github.com/hfiref0x/UACME
    - https://winscripting.blog/2017/05/12/first-entry-welcome-and-uac-bypass/
    - https://github.com/RhinoSecurityLabs/Aggressor-Scripts/tree/master/UACBypass
    - https://tria.ge/211119-gs7rtshcfr/behavioral2 [Lokibot sample from Nov 2021]
author: Christian Burkard (Nextron Systems)
date: 2021-08-30
modified: 2022-01-13
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.t1548.002
    - attack.t1546.001
logsource:
    category: registry_event
    product: windows
detection:
    selection1:
        EventType: SetValue
        TargetObject|endswith: 'Classes\ms-settings\shell\open\command\SymbolicLinkValue'
        Details|contains: '\Software\Classes\{'
    selection2:
        TargetObject|endswith: 'Classes\ms-settings\shell\open\command\DelegateExecute'
    selection3:
        EventType: SetValue
        TargetObject|endswith:
            - 'Classes\ms-settings\shell\open\command\(Default)'
            - 'Classes\exefile\shell\open\command\(Default)'
    filter_sel3:
        Details: '(Empty)'
    condition: selection1 or selection2 or (selection3 and not filter_sel3)
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection1 or selection2 or (selection3 and not filter_sel3)

Stage 1: `selection1`

selection1:
    EventType: SetValue
    TargetObject|endswith: 'Classes\ms-settings\shell\open\command\SymbolicLinkValue'
    Details|contains: '\Software\Classes\{'

Stage 2: `selection2`

selection2:
    TargetObject|endswith: 'Classes\ms-settings\shell\open\command\DelegateExecute'

Stage 3: `selection3`

selection3:
    EventType: SetValue
    TargetObject|endswith:
        - 'Classes\ms-settings\shell\open\command\(Default)'
        - 'Classes\exefile\shell\open\command\(Default)'

Stage 4: `not filter_sel3`

filter_sel3:
    Details: '(Empty)'

Exclusions

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

Field	Kind	Excluded values
`Details`	eq	`(Empty)`

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	`\Software\Classes\{`
`EventType`	eq	`SetValue` corpus 6 (sigma 6)
`TargetObject`	ends_with	`Classes\exefile\shell\open\command\(Default)` `Classes\ms-settings\shell\open\command\(Default)` `Classes\ms-settings\shell\open\command\DelegateExecute` `Classes\ms-settings\shell\open\command\SymbolicLinkValue`

`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)

Shell Open Registry Keys Manipulation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection1`

Stage 2: `selection2`

Stage 3: `selection3`

Stage 4: `not filter_sel3`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Shell Open Registry Keys Manipulation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection1

Stage 2: selection2

Stage 3: selection3

Stage 4: not filter_sel3

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection1`

Stage 2: `selection2`

Stage 3: `selection3`

Stage 4: `not filter_sel3`