LummaStealer está cobrando una segunda vida junto a CastleLoader

Ruslan Mikhalov Jefe de Investigación de Amenazas en SOC Prime

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LummaStealer está cobrando una segunda vida junto a CastleLoader

Detection stack

AIDR
Alert
ETL
Query

Informe de Amenazas
Flujo de Ataque
Detecciones
Simulaciones

Resumen

LummaStealer es un infostealer que ha resurgido tras una importante interrupción por parte de las fuerzas del orden en 2025. La actividad reciente pivota hacia CastleLoader, un cargador basado en scripts que entrega LummaStealer a través de señuelos de ingeniería social como software “cracked” falso y páginas CAPTCHA falsas. La cadena enfatiza la ejecución en memoria, la ofuscación agresiva y la infraestructura compartida entre ambas familias de malware. Los defensores pueden priorizar la búsqueda de comportamientos DNS inusuales, AutoIt rastros de ejecución y patrones comunes de persistencia.

Investigación

Los investigadores de Bitdefender analizaron muestras frescas y confirmaron CastleLoader como el principal mecanismo de entrega de LummaStealer. Escrito en AutoIt, el cargador realiza verificaciones de sandbox, establece persistencia en Local AppData, y genera una señal de red distintiva mediante repetidas consultas DNS fallidas. Los analistas también notaron superposición de infraestructura con los servicios vinculados a GrayBravo. Se extrajeron cadenas de línea de comandos relevantes y fragmentos de código para apoyar el desarrollo de reglas de detección.

Mitigación

Reduzca la exposición bloqueando las descargas de software pirateado, instaladores de juegos y otros paquetes de medios no confiables. Prevenga o controle estrictamente la ejecución de AutoIt scripts desconocidos y monitoree la creación de archivos bajo rutas nombradas CraftStitch Studios Inc. Implemente MFA y rote credenciales después de una sospecha de compromiso. Aplique controles de red para marcar o bloquear las consultas DNS fallidas características y la infraestructura IP maliciosa asociada.

Respuesta

Si se encuentran artefactos de CastleLoader o LummaStealer, aísle el host, detenga los AutoIt procesos sospechosos y elimine artefactos de persistencia de. Preserve evidencias recopilando la carga útil descargada, telemetría de red relevante y cualquier acceso directo creado. Restablezca las credenciales expuestas e invalide las sesiones de navegador activas. Actualice las detecciones utilizando los IOCs extraídos para identificar hosts adicionales afectados.

"graph TB %% Class definitions classDef action fill:#99ccff classDef tool fill:#ffcc99 classDef malware fill:#ff9999 classDef operator fill:#ff9900 classDef builtin fill:#cccccc %% Nodes u2013 Initial Access init_user_execution["Acción – T1204 Ejecución del Usuario: Las víctimas ejecutan software o instaladores de juegos/películas «cracks» falsos. Descripción: Ejecución de código malicioso por parte del usuario."] class init_user_execution action init_mal_copy_paste["Acción – T1204.004 Copiar y Pegar Malicioso: Los usuarios siguen las instrucciones CAPTCHA de ClickFix para copiar y pegar comandos maliciosos. Descripción: El atacante guía a la víctima a ejecutar código controlado por el atacante."] class init_mal_copy_paste action %% Nodes u2013 Loader Deployment loader_autoit["Herramienta – T1059.010 Intérprete de AutoIt: Script compilado de CastleLoader. Descripción: Ejecuta código AutoIt fuertemente ofuscado."] class loader_autoit tool obfuscation["Acción – T1027.009 Cargas Útiles Incrustadas: El script AutoIt ofuscado oculta la carga útil maliciosa. Descripción: Usa codificación y empaquetado para evadir el análisis."] class obfuscation action masquerading["Acción – T1036 Menospreciar: El cargador se disfraza como un instalador legítimo con extensiones de software comunes. Descripción: Parece benigno al usuario y herramientas de seguridad."] class masquerading action %% Nodes u2013 Persistence persistence_shortcut["Acción – T1547.009 Modificación de Accesos Directos: Crea archivos .lnk y .url en la carpeta de Inicio. Descripción: Persiste al iniciarse durante el inicio de sesión del usuario."] class persistence_shortcut action persistence_task["Acción – T1053 Tarea Programada: El script VBA registra una tarea programada para ejecución repetida. Descripción: Ejecuta la carga útil en intervalos definidos."] class persistence_task action persistence_init["Acción – T1037 Scripts de Inicialización de Inicio de Sesión and T1547.014 Configuración Activa: Ejecuta scripts durante el inicio de sesión del usuario a través de claves de registro. Descripción: Asegura que el código se ejecute en cada inicio de sesión."] class persistence_init action hijack_execution["Acción – T1574 Secuestrar Flujo de Ejecución: Carga reflexiva de la carga útil maliciosa en la memoria. Descripción: Se ejecuta sin escribir archivos en el disco."] class hijack_execution action %% Nodes u2013 Defense Evasion defense_virtual["Acción – T1497 Evasión de Virtualización/Sandbox y T1497.002 Verificaciones de Actividad de Usuario: Detecta el entorno de análisis y aborta la ejecución. Descripción: Evita la detección de sandbox."] class defense_virtual action defense_reflective["Acción – T1620 Carga Reflexiva de Código: Carga código a través de reflexión para ocultar actividad. Descripción: Evita herramientas de análisis estático."] class defense_reflective action %% Nodes u2013 Command and Control c2_dga["Acción – T1568.002 Algoritmos de Generación de Dominios: Genera dominios pseudo-aleatorios causando consultas DNS fallidas. Descripción: Proporciona puntos finales C2 dinámicos."] class c2_dga action c2_dns["Acción – T1071.004 Protocolo DNS: Comunica a través de consultas y respuestas DNS. Descripción: Usa DNS en capa de aplicación para C2."] class c2_dns action c2_web["Acción – T1102 Servicio Web: Comunicación bidireccional a través de servicio web HTTPS. Descripción: Sirve como canal principal C2."] class c2_web action %% Nodes u2013 Credential Access cred_browser["Acción – T1555.003 Credenciales de Navegadores Web: Roba contraseñas almacenadas, archivos de criptomonedero y datos de sesión. Descripción: Extrae credenciales de Chrome, Firefox, etc."] class cred_browser action cred_cookie["Acción – T1550.004 Cookie de Sesión Web: Usa cookies robadas como material de autenticación alternativo. Descripción: Reutiliza sesiones web válidas."] class cred_cookie action forge_cookie["Acción – T1606.001 Forjar Credenciales Web: Crea cookies falsificadas para suplantar a las víctimas. Descripción: Permite acceso no autorizado a servicios web."] class forge_cookie action %% Nodes u2013 Exfiltration exfil_c2["Acción – T1041 Exfiltración sobre Canal C2: Envía datos recolectados a través del servicio web C2. Descripción: Los datos salen de la red a través del mismo canal utilizado para comando y control."] class exfil_c2 action %% Connections u2013 Attack Flow init_user_execution –>|lleva_a| loader_autoit init_mal_copy_paste –>|lleva_a| loader_autoit loader_autoit –>|usa| obfuscation loader_autoit –>|se_disfraza_como| masquerading loader_autoit –>|establece| persistence_shortcut loader_autoit –>|establece| persistence_task loader_autoit –>|establece| persistence_init persistence_shortcut –>|habilita| hijack_execution persistence_task –>|habilita| hijack_execution persistence_init –>|habilita| hijack_execution hijack_execution –>|emplea| defense_virtual hijack_execution –>|emplea| defense_reflective hijack_execution –>|conecta_a| c2_dga c2_dga –>|resuelve_a_través_de| c2_dns c2_dns –>|comunica_a_través_de| c2_web c2_web –>|roba| cred_browser c2_web –>|captura| cred_cookie c2_web –>|habilita| forge_cookie cred_browser –>|proporciona| exfil_c2 cred_cookie –>|proporciona| exfil_c2 forge_cookie –>|proporciona| exfil_c2 %% Estilo class init_user_execution,init_mal_copy_paste action class loader_autoit,obfuscation,masquerading tool class persistence_shortcut,persistence_task,persistence_init,hijack_execution,defense_virtual,defense_reflective,cred_browser,cred_cookie,forge_cookie action class c2_dga,c2_dns,c2_web,exfil_c2 action "

Flujo de Ataque

Narrativa del Ataque y Comandos:
1. Caída Inicial: El atacante obtiene el contexto del usuario (por ejemplo, a través de phishing) y usa el explorer.exe proceso legítimo para lanzar la carga útil maliciosa ubicada en un recurso compartido de red montado: DeviceHarddiskVolumeXNFSNeed for Speed Hot PursuitSetup.exe.
2. Persistencia y Lanzador: Después de que el malicioso Setup.exe se ejecuta, se deja caer un script por lotes (Pros.cmd) en el mismo directorio. El atacante luego utiliza cmd.exe /c copy Pros Pros.cmd & Pros.cmd para ejecutar el script, que carga cargas útiles adicionales.
3. Proxy de AutoIt: En paralelo, el cargador puede invocar AutoIt3.exe con un script incrustado (V.a3x) para eludir AppLocker. Esto refleja la condition selection_autoit .
Estos pasos generan los tres patrones exactos de telemetría requeridos por la regla Sigma:
- explorer.exe con la ruta fija de Setup.exe malicioso, and
- cmd.exe con /c además de ya sea una cadena de copiar y ejecutar or una ejecución de AutoIt.

Script de Prueba de Regresión:

# -----------------------------------------------
# Script de simulación de LummaStealer / CastleLoader
# -----------------------------------------------
$maliciousDir = "$env:ProgramDataNFSNeed for Speed Hot Pursuit"
$setupPath    = Join-Path $maliciousDir "Setup.exe"
$batchPath    = Join-Path $maliciousDir "Pros.cmd"
$autoItPath   = Join-Path $maliciousDir "V.a3x"

# 1. Crear estructura de directorios
New-Item -Path $maliciousDir -ItemType Directory -Force | Out-Null

# 2. Colocar archivos maliciosos ficticios (archivos vacíos son suficientes para el registro)
New-Item -Path $setupPath    -ItemType File -Force | Out-Null
New-Item -Path $batchPath    -ItemType File -Force | Out-Null
New-Item -Path $autoItPath   -ItemType File -Force | Out-Null

# 3. Simular explorer.exe lanzando el malicioso Setup.exe
Start-Process -FilePath "explorer.exe" -ArgumentList $setupPath

# Pequeña pausa para asegurar que el primer evento esté registrado
Start-Sleep -Seconds 2

# 4a. Activar la cadena de copiar y ejecutar de cmd.exe
cmd.exe /c "copy Pros.cmd $batchPath & $batchPath"

# 4b. (Alternativa) Activar ejecución de AutoIt – descomentar si se prueba este camino
# Start-Process -FilePath "AutoIt3.exe" -ArgumentList $autoItPath

# 5. Esperar que los eventos fluyan al SIEM
Start-Sleep -Seconds 5

Comandos de Limpieza:

# Eliminar todos los artefactos creados por la simulación
Remove-Item -Path "$env:ProgramDataNFS" -Recurse -Force -ErrorAction SilentlyContinue

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Name	Descripiton
PHPSESSID	Preserves user session state across page requests. Cookie generated by applications based on the PHP language. This is a general purpose identifier used to maintain user session variables. It is normally a random generated number, how it is used can be specific to the site, but a good example is maintaining a logged-in status for a user between pages.
sp_i	Used to store information about authenticated User.
sp_r	Used to store information about authenticated User.
sp_a	Used to store information about authenticated User.

Name	Descripiton
tuuid	Collects anonymous data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded.
tuuid_last_update	Collects anonymous data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded.
um	Collects anonymous data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded.
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na_sc_x	Used by the social sharing platform AddThis to keep a record of parts of the site that has been visited in order to recommend other parts of the site.
APID	Collects anonymous data related to the user's visits to the website.
IDSYNC	Collects anonymous data related to the user's visits to the website.
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_cc_cc	Collects anonymous statistical data related to the user's website visits, such as the number of visits, average time spent on the website and what pages have been loaded. The purpose is to segment the website's users according to factors such as demographics and geographical location, in order to enable media and marketing agencies to structure and understand their target groups to enable customised online advertising.
_cc_dc	Collects anonymous statistical data related to the user's website visits, such as the number of visits, average time spent on the website and what pages have been loaded. The purpose is to segment the website's users according to factors such as demographics and geographical location, in order to enable media and marketing agencies to structure and understand their target groups to enable customised online advertising.
_cc_id	Collects anonymous statistical data related to the user's website visits, such as the number of visits, average time spent on the website and what pages have been loaded. The purpose is to segment the website's users according to factors such as demographics and geographical location, in order to enable media and marketing agencies to structure and understand their target groups to enable customised online advertising.
dpm	Via a unique ID that is used for semantic content analysis, the user's navigation on the website is registered and linked to offline data from surveys and similar registrations to display targeted ads.
acs	Collects anonymous data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded, with the purpose of displaying targeted ads.
clid	Collects anonymous data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded, with the purpose of displaying targeted ads.
KRTBCOOKIE_#	Registers a unique ID that identifies the user's device during return visits across websites that use the same ad network. The ID is used to allow targeted ads.
PUBMDCID	Registers a unique ID that identifies the user's device during return visits across websites that use the same ad network. The ID is used to allow targeted ads.
PugT	Registers a unique ID that identifies the user's device during return visits across websites that use the same ad network. The ID is used to allow targeted ads.
ssi	Registers a unique ID that identifies a returning user's device. The ID is used for targeted ads.
_tmid	Registers a unique ID that identifies the user's device upon return visits. The ID is used to target ads in video clips.
wam-sync	Used by the advertising platform Weborama to determine the visitor's interests based on pages visits, content clicked and other actions on the website.
wui	Used by the advertising platform Weborama to determine the visitor's interests based on pages visits, content clicked and other actions on the website.
AFFICHE_W	Used by the advertising platform Weborama to determine the visitor's interests based on pages visits, content clicked and other actions on the website.
B	Collects anonymous data related to the user's website visits, such as the number of visits, average time spent on the website and what pages have been loaded. The registered data is used to categorise the users' interest and demographical profiles with the purpose of customising the website content depending on the visitor.
1P_JAR	These cookies are used to gather website statistics, and track conversion rates.
APISID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
HSID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
NID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
SAPISID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
SID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
SIDCC	Security cookie to protect users data from unauthorised access.
SSID	Google set a number of cookies on any page that includes a Google reCAPTCHA. While we have no control over the cookies set by Google, they appear to include a mixture of pieces of information to measure the number and behaviour of Google reCAPTCHA users.
__utmx	This cookie is associated with Google Website Optimizer, a tool designed to help site owners improve their wbesites. It is used to distinguish between two varaitions a webpage that might be shown to a visitor as part of an A/B split test. This helps site owners to detemine which version of a page performs better, and therefore helps to improve the website.
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Name	Descripiton
_hjid	Hotjar cookie. This cookie is set when the customer first lands on a page with the Hotjar script. It is used to persist the random user ID, unique to that site on the browser. This ensures that behavior in subsequent visits to the same site will be attributed to the same user ID.
_hjIncludedInSample	This cookie is associated with web analytics functionality and services from Hot Jar, a Malta based company. It uniquely identifies a visitor during a single browser session and indicates they are included in an audience sample.
intercom-id-[xxx]	This cookie is used by Intercom as a session so that users can continue a chat as they move through the site.
intercom-session-[xxx]	Used to keeping track of sessions and remember logins and conversations.
demdex	Via a unique ID that is used for semantic content analysis, the user's navigation on the website is registered and linked to offline data from surveys and similar registrations to display targeted ads.
CookieConsent	Stores the user's cookie consent state for the current domain.
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Name	Descripiton
_ga	This cookie name is asssociated with Google Universal Analytics - which is a significant update to Google's more commonly used analytics service. This cookie is used to distinguish unique users by assigning a randomly generated number as a client identifier. It is included in each page. Registers a unique ID that is used to generate statistical data on how the visitor uses the website. request in a site and used to calculate visitor, session and campaign data for the sites analytics reports. By default it is set to expire after 2 years, although this is customisable by website owners.
_gat	Used by Google Analytics to throttle request rate. This cookie name is associated with Google Universal Analytics, according to documentation it is used to throttle the request rate - limiting the collection of data on high traffic sites. It expires after 10 minutes.
_gid	This cookie name is asssociated with Google Universal Analytics. This appears to be a new cookie and as of Spring 2017 no information is available from Google. It appears to store and update a unique value for each page visited. Registers a unique ID that is used to generate statistical data on how the visitor uses the website.
IDE	Used by Google DoubleClick to register and report the website user's actions after viewing or clicking one of the advertiser's ads with the purpose of measuring the efficacy of an ad and to present targeted ads to the user.
r/collect	Used by Google DoubleClick to register and report the website user's actions after viewing or clicking one of the advertiser's ads with the purpose of measuring the efficacy of an ad and to present targeted ads to the user.
test_cookie	Used to check if the user's browser supports cookies.
collect	Used to send data to Google Analytics about the visitor's device and behaviour. Tracks the visitor across devices and marketing channels.
ads/user-lists/#	These cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites.
c	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.
khaos	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.
put_#	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.
rpb	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.
rpx	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.
tap.php	Registers anonymised user data, such as IP address, geographical location, visited websites, and what ads the user has clicked, with the purpose of optimising ad display based on the user's movement on websites that use the same ad network.