Command Executed Via Run Dialog Box - Registry

Status: test
Severity: low
Author: Ahmed Farouk, Nasreddine Bencherchali
Source: github.com/SigmaHQ/sigma

Detects execution of commands via the run dialog box on Windows by checking values of the "RunMRU" registry key. This technique was seen being abused by threat actors to deceive users into pasting and executing malicious commands, often disguised as CAPTCHA verification steps.

Event coverage

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

Rule body yaml

title: Command Executed Via Run Dialog Box - Registry
id: f9d091f6-f1c7-4873-a24f-050b4a02b4dd
related:
    - id: a7df0e9e-91a5-459a-a003-4cde67c2ff5d
      type: derived
status: test
description: |
    Detects execution of commands via the run dialog box on Windows by checking values of the "RunMRU" registry key.
    This technique was seen being abused by threat actors to deceive users into pasting and executing malicious commands, often disguised as CAPTCHA verification steps.
references:
    - https://www.forensafe.com/blogs/runmrukey.html
    - https://medium.com/@shaherzakaria8/downloading-trojan-lumma-infostealer-through-capatcha-1f25255a0e71
    - https://redcanary.com/blog/threat-intelligence/intelligence-insights-october-2024/
author: Ahmed Farouk, Nasreddine Bencherchali
date: 2024-11-01
tags:
    - detection.threat-hunting
    - attack.execution
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains: '\Microsoft\Windows\CurrentVersion\Explorer\RunMRU'
    filter_main_mrulist:
        TargetObject|endswith: '\MRUList'
    filter_optional_ping:
        Details|contains: 'ping'
    filter_optional_generic:
        Details:
            - '%appdata%\1'
            - '%localappdata%\1'
            - '%public%\1'
            - '%temp%\1'
            - 'calc\1'
            - 'dxdiag\1'
            - 'explorer\1'
            - 'gpedit.msc\1'
            - 'mmc\1'
            - 'notepad\1'
            - 'regedit\1'
            - 'services.msc\1'
            - 'winver\1'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Likely
level: low

Stages and Predicates

Stage 0: `condition`

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

Stage 1: `selection`

selection:
    TargetObject|contains: '\Microsoft\Windows\CurrentVersion\Explorer\RunMRU'

Stage 2: `not filter_main_mrulist`

filter_main_mrulist:
    TargetObject|endswith: '\MRUList'

Stage 3: `not filter_optional_*`

filter_optional_ping:
    Details|contains: 'ping'
filter_optional_generic:
    Details:
        - '%appdata%\1'
        - '%localappdata%\1'
        - '%public%\1'
        - '%temp%\1'
        - 'calc\1'
        - 'dxdiag\1'
        - 'explorer\1'
        - 'gpedit.msc\1'
        - 'mmc\1'
        - 'notepad\1'
        - 'regedit\1'
        - 'services.msc\1'
        - 'winver\1'

Exclusions

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

Stage	Field	Kind	Excluded values
2	`TargetObject`	ends_with	`\MRUList`
3	`Details`	eq	`%appdata%\1`
3	`Details`	eq	`%localappdata%\1`
3	`Details`	eq	`%public%\1`
3	`Details`	eq	`%temp%\1`
3	`Details`	eq	`calc\1`
3	`Details`	eq	`dxdiag\1`
3	`Details`	eq	`explorer\1`
3	`Details`	eq	`gpedit.msc\1`
3	`Details`	eq	`mmc\1`
3	`Details`	eq	`notepad\1`
3	`Details`	eq	`regedit\1`
3	`Details`	eq	`services.msc\1`
3	`Details`	eq	`winver\1`
3	`Details`	match	`ping`

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	`\Microsoft\Windows\CurrentVersion\Explorer\RunMRU` 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:`)
`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)

Command Executed Via Run Dialog Box - Registry

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_mrulist`

Stage 3: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Command Executed Via Run Dialog Box - Registry

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_mrulist

Stage 3: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_mrulist`

Stage 3: `not filter_optional_*`