Privilege escalation via RunasCS

Status: experimental
Severity: low
Log source: product windows, category process_creation
Author: mdecrevoisier
Source: github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where attack attempts to elevate privileges via customize Runas tool.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1134.002` Access Token Manipulation: Create Process with Token

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4688	A new process has been created.

Rule body yaml

title: Privilege escalation via RunasCS
description: Detects scenarios where attack attempts to elevate privileges via customize Runas tool.
correlation: correlation with ID 4648 can be done over SubjectLogonId in order to get more context.
references:
- https://github.com/mdecrevoisier/EVTX-to-MITRE-Attack/tree/master/TA0004-Privilege%20Escalation/T1134-Access%20Token%20Manipulation
- https://github.com/antonioCoco/RunasCs
- https://twitter.com/SBousseaden/status/1478373779642400783
tags:
- attack.privilege_escalation
- attack.t1134.002
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  category: process_creation
detection:

  selection_process: # optional parameter with suspicious behavior reported by SBousseaden
    EventID: 4688
    TargetUserSid: S-1-0-0 # everyone

  filter_user_process:
    - TargetUserName:
      - 'LOCAL SERVICE'
      - 'Network Service'
      - 'DWM-*'
      - 'UMFD-*'
      - 'sshd_*'
      - '*$'
      - 'DefaultAppPool'
      - '-'
    - TargetDomainName:
      - 'NT Service'
      - 'NT AUTHORITY'
      - 'Font Driver Host'
      - 'Window Manager'
      - 'IIS APPPOOL'
      - 'VIRTUAL USERS'

  condition: selection_process and not filter_user_process
falsepositives:
- Administrator activity
level: low

Stages and Predicates

Stage 0: `condition`

selection_process and not filter_user_process

Stage 1: `selection_process`

selection_process:
  EventID: 4688
  TargetUserSid: S-1-0-0

Stage 2: `not filter_user_process`

filter_user_process:
  - TargetUserName:
    - 'LOCAL SERVICE'
    - 'Network Service'
    - 'DWM-*'
    - 'UMFD-*'
    - 'sshd_*'
    - '*$'
    - 'DefaultAppPool'
    - '-'
  - TargetDomainName:
    - 'NT Service'
    - 'NT AUTHORITY'
    - 'Font Driver Host'
    - 'Window Manager'
    - 'IIS APPPOOL'
    - 'VIRTUAL USERS'

Exclusions

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

Field	Kind	Excluded values
`TargetDomainName`	eq	`Font Driver Host`
`TargetDomainName`	eq	`IIS APPPOOL`
`TargetDomainName`	eq	`NT AUTHORITY`
`TargetDomainName`	eq	`NT Service`
`TargetDomainName`	eq	`VIRTUAL USERS`
`TargetDomainName`	eq	`Window Manager`
`TargetUserName`	eq	`*$`
`TargetUserName`	eq	`-`
`TargetUserName`	eq	`DWM-*`
`TargetUserName`	eq	`DefaultAppPool`
`TargetUserName`	eq	`LOCAL SERVICE`
`TargetUserName`	eq	`Network Service`
`TargetUserName`	eq	`UMFD-*`
`TargetUserName`	eq	`sshd_*`

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
`TargetUserSid`	eq	`S-1-0-0`

`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)

Privilege escalation via RunasCS

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_process`

Stage 2: `not filter_user_process`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Privilege escalation via RunasCS

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_process

Stage 2: not filter_user_process

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_process`

Stage 2: `not filter_user_process`