Rhadamanthys Stealer Module Launch Via Rundll32.EXE

Status: test
Severity: medium
Log source: product windows, category process_creation
Author: TropChaud
Source: github.com/SigmaHQ/sigma

Detects the use of Rundll32 to launch an NSIS module that serves as the main stealer capability of Rhadamanthys infostealer, as observed in reports and samples in early 2023

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218.011` System Binary Proxy Execution: Rundll32

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Rhadamanthys Stealer Module Launch Via Rundll32.EXE
id: 5cdbc2e8-86dd-43df-9a1a-200d4745fba5
status: test
description: Detects the use of Rundll32 to launch an NSIS module that serves as the main stealer capability of Rhadamanthys infostealer, as observed in reports and samples in early 2023
references:
    - https://elis531989.medium.com/dancing-with-shellcodes-analyzing-rhadamanthys-stealer-3c4986966a88
    - https://blog.cyble.com/2023/01/12/rhadamanthys-new-stealer-spreading-through-google-ads/
    - https://www.joesandbox.com/analysis/790122/0/html
    - https://twitter.com/anfam17/status/1607477672057208835
author: TropChaud
date: 2023-01-26
modified: 2023-02-05
tags:
    - attack.stealth
    - attack.t1218.011
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection_rundll32:
        - OriginalFileName: 'RUNDLL32.EXE'
        - Image|endswith: '\rundll32.exe'
    selection_dll:
        CommandLine|contains: 'nsis_uns'
    selection_export_function:
        CommandLine|contains: 'PrintUIEntry'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_rundll32`

selection_rundll32:
    - OriginalFileName: 'RUNDLL32.EXE'
    - Image|endswith: '\rundll32.exe'

Stage 2: `selection_dll`

selection_dll:
    CommandLine|contains: 'nsis_uns'

Stage 3: `selection_export_function`

selection_export_function:
    CommandLine|contains: 'PrintUIEntry'

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	`PrintUIEntry` `nsis_uns`
`Image`	ends_with	`\rundll32.exe` corpus 95 (sigma 95)
`OriginalFileName`	eq	`RUNDLL32.EXE` corpus 62 (sigma 35, splunk 21, elastic 6)

`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)

Rhadamanthys Stealer Module Launch Via Rundll32.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_rundll32`

Stage 2: `selection_dll`

Stage 3: `selection_export_function`

Indicators

Keyboard shortcuts

Search operators

Rhadamanthys Stealer Module Launch Via Rundll32.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_rundll32

Stage 2: selection_dll

Stage 3: selection_export_function

Indicators

Stage 0: `condition`

Stage 1: `selection_rundll32`

Stage 2: `selection_dll`

Stage 3: `selection_export_function`