O futuro do Zero Trust e do SASE é agora! Assista sob demanda

fechar
fechar
  • Por que Netskope chevron

    Mudando a forma como a rede e a segurança trabalham juntas.

  • Nossos clientes chevron

    A Netskope atende a mais de 3.000 clientes em todo o mundo, incluindo mais de 25 das empresas da Fortune 100

  • Nossos parceiros chevron

    Fazemos parceria com líderes de segurança para ajudá-lo a proteger sua jornada para a nuvem.

O mais alto nível de Execução. A Visão mais avançada.

A Netskope foi reconhecida como Líder no Magic Quadrant™ do Gartner® de 2023 para SSE.

Obtenha o Relatório
A Netskope foi reconhecida como Líder no Magic Quadrant™ do Gartner® de 2023 para SSE.
Ajudamos nossos clientes a estarem prontos para tudo

Veja nossos clientes
Woman smiling with glasses looking out window
A estratégia de comercialização da Netskope, focada em Parcerias, permite que nossos Parceiros maximizem seu crescimento e lucratividade enquanto transformam a segurança corporativa.

Saiba mais sobre os parceiros da Netskope
Group of diverse young professionals smiling
Sua Rede do Amanhã

Planeje seu caminho rumo a uma rede mais rápida, segura e resiliente projetada para os aplicativos e usuários aos quais você oferece suporte.

Receba o whitepaper
Sua Rede do Amanhã
Apresentando a plataforma Netskope One

O Netskope One é uma plataforma nativa da nuvem que oferece serviços convergentes de segurança e rede para permitir sua transformação SASE e zero trust.

Saiba mais sobre o Netskope One
Abstrato com iluminação azul
Adote uma arquitetura Secure Access Service Edge (SASE)

O Netskope NewEdge é a maior nuvem privada de segurança de alto desempenho do mundo e oferece aos clientes cobertura de serviço, desempenho e resiliência inigualáveis.

Conheça a NewEdge
NewEdge
Netskope Cloud Exchange

O Cloud Exchange (CE) da Netskope oferece aos clientes ferramentas de integração poderosas para tirar proveito dos investimentos em estratégias de segurança.

Saiba mais sobre o Cloud Exchange
Vídeo da Netskope
A plataforma do futuro é a Netskope

Intelligent Security Service Edge (SSE), Cloud Access Security Broker (CASB), Cloud Firewall, Next Generation Secure Web Gateway (SWG) e Private Access for ZTNA integrados nativamente em uma única solução para ajudar todas as empresas em sua jornada para o Secure Access Service Arquitetura de borda (SASE).

Vá para a plataforma
Vídeo da Netskope
Next Gen SASE Branch é híbrida — conectada, segura e automatizada

Netskope Next Gen SASE Branch converge o Context-Aware SASE Fabric, Zero-Trust Hybrid Security e SkopeAI-Powered Cloud Orchestrator em uma oferta de nuvem unificada, inaugurando uma experiência de filial totalmente modernizada para empresas sem fronteiras.

Saiba mais sobre Next Gen SASE Branch
Pessoas no escritório de espaço aberto
Desenvolvendo uma Arquitetura SASE para Leigos

Obtenha sua cópia gratuita do único guia de planejamento SASE que você realmente precisará.

Baixe o eBook
Mude para serviços de segurança na nuvem líderes de mercado com latência mínima e alta confiabilidade.

Conheça a NewEdge
Lighted highway through mountainside switchbacks
Permita com segurança o uso de aplicativos generativos de IA com controle de acesso a aplicativos, treinamento de usuários em tempo real e a melhor proteção de dados da categoria.

Saiba como protegemos o uso de IA generativa
Ative com segurança o ChatGPT e a IA generativa
Soluções de zero trust para a implementação de SSE e SASE

Conheça o Zero Trust
Boat driving through open sea
Netskope obtém alta autorização do FedRAMP

Escolha o Netskope GovCloud para acelerar a transformação de sua agência.

Saiba mais sobre o Netskope GovCloud
Netskope GovCloud
  • Recursos chevron

    Saiba mais sobre como a Netskope pode ajudá-lo a proteger sua jornada para a nuvem.

  • Blog chevron

    Saiba como a Netskope permite a transformação da segurança e da rede por meio do SSE (Security Service Edge)

  • Eventos e workshops chevron

    Esteja atualizado sobre as últimas tendências de segurança e conecte-se com seus pares.

  • Security Defined chevron

    Tudo o que você precisa saber em nossa enciclopédia de segurança cibernética.

Podcast Security Visionaries

How to Use a Magic Quadrant and Other Industry Research
Neste episódio, Max Havey, Steve Riley e Mona Faulkner analisam o intrincado processo de criação de um Magic Quadrant e por que ele é muito mais do que apenas um gráfico.

Reproduzir o podcast
Como usar um Quadrante Mágico e outros podcasts de pesquisa do setor
Últimos blogs

Leia como a Netskope pode viabilizar a jornada Zero Trust e SASE por meio de recursos de borda de serviço de segurança (SSE).

Leia o Blog
Sunrise and cloudy sky
SASE Week 2023: Sua jornada SASE começa agora!

Replay das sessões da quarta SASE Week anual.

Explorar sessões
SASE Week 2023
O que é o Security Service Edge?

Explore o lado de segurança de SASE, o futuro da rede e proteção na nuvem.

Saiba mais sobre o Security Service Edge
Four-way roundabout
  • Empresa chevron

    Ajudamos você a antecipar os desafios da nuvem, dos dados e da segurança da rede.

  • Liderança chevron

    Nossa equipe de liderança está fortemente comprometida em fazer tudo o que for preciso para tornar nossos clientes bem-sucedidos.

  • Customer Solutions chevron

    Estamos aqui junto com você a cada passo da sua trajetória, assegurando seu sucesso com a Netskope.

  • Treinamento e certificação chevron

    Os treinamentos da Netskope vão ajudar você a ser um especialista em segurança na nuvem.

Apoiando a sustentabilidade por meio da segurança de dados

A Netskope tem o orgulho de participar da Visão 2045: uma iniciativa destinada a aumentar a conscientização sobre o papel da indústria privada na sustentabilidade.

Saiba mais
Apoiando a sustentabilidade por meio da segurança de dados
Pensadores, construtores, sonhadores, inovadores. Juntos, fornecemos soluções de segurança na nuvem de última geração para ajudar nossos clientes a proteger seus dados e seu pessoal.

Conheça nossa equipe
Group of hikers scaling a snowy mountain
A talentosa e experiente equipe de Serviços Profissionais da Netskope fornece uma abordagem prescritiva para sua implementação bem sucedida.

Conheça os Serviços Profissionais
Netskope Professional Services
Proteja sua jornada de transformação digital e aproveite ao máximo seus aplicativos de nuvem, web e privados com o treinamento da Netskope.

Saiba mais sobre Treinamentos e Certificações
Group of young professionals working

Ousaban: LATAM Banking Malware Abusing Cloud Services

Aug 04 2022

Sumário

Ousaban (a.k.a. Javali) is a banking malware that emerged between 2017 and 2018, with the primary goal of stealing sensitive data from financial institutions in Brazil. This malware is developed in Delphi and it comes from a stream of LATAM banking trojans sourced from Brazil, sharing similarities with other families like Guildma, Casbaneiro, and Grandoreiro. Furthermore, the threat often abuses cloud services, such as Amazon S3 to download second stage payloads, and Google Docs to retrieve the C2 configuration.

Netskope Threat Labs came across recent Ousaban samples that are abusing multiple cloud services throughout the attack flow, such as Amazon or Azure to download its payloads and log the victim’s IP, and Pastebin to retrieve the C2 configuration. The malware is downloaded through MSI files either by a JavaScript or a Delphi DLL, and is targeting more than 50 financial institutions in Brazil. Furthermore, we also found Telegram abuse in the malware code, likely used for C2 communication via Webhooks.

Diagram of Ousaban attack flow

In this blog post, we will analyze Ousaban, showing its delivery methods, obfuscation techniques, and C2 communication.

Delivery methods

Ousaban is delivered through malicious MSI files spread in phishing emails. In this campaign, we found that the MSI file downloads and executes the second stage either through JavaScript or a PE file.

Delivery by JavaScript
In the first scenario, the JavaScript is executed via CustomAction.

Example of MSI file executing JavaScript.
MSI file executing JavaScript.

The JavaScript code is obfuscated, likely in an attempt to slow down analysis.

Example of JavaScript code extracted from the MSI file
JavaScript code extracted from the MSI file

Looking at the deobfuscated code, these are the steps executed by the malware:

  1. Creates an empty file to be used as a flag in case the MSI is executed twice (similar concept as Mutex usage);
  2. Downloads the second stage from the cloud, either from Amazon or Azure;
  3. Decompress the ZIP file downloaded from the cloud and renames the main executable;
  4. Sends a simple GET request to another URL (Azure or another attacker-controlled server), alerting the attacker and logging the victim’s IP;
  5. Executes the main file via WMIC.
Screenshot of deobfuscated JavaScript extracted from the MSI file.
Deobfuscated JavaScript extracted from the MSI file.

Delivery by File

We also found Ousaban being delivered without JavaScript. In this case, we can see a file named “avisoProtesto.exe” being executed via MSI CustomAction.

Example of MSI executing a PE file.
MSI executing a PE file.

“avisoProtesto.exe” is a signed and non-malicious binary exploited to execute the malicious DLL via DLL search order hijacking.

Example of non-malicious binary used to load the malicious DLL.
Non-malicious binary used to load the malicious DLL.

This is possible because the non-malicious binary loads a DLL named “crashreport.dll” without specifying the real path of the library. Therefore, the attacker places a DLL with the same name in the same folder of the executable, making it load the malicious DLL instead.

Example of Binary vulnerable to DLL hijacking.
Binary vulnerable to DLL hijacking.

In this case, both next-stage and tracker URL are loaded from a text file, named “FileLinks”.

Screenshot of malicious URLs loaded by the malware.
Malicious URLs loaded by the malware.

All the files we analyzed were downloading the next stage from the cloud, either Amazon or Azure. In some cases, the URL used to log the victim’s IP address was also from Azure. All the URLs can be found in our GitHub repository.

Loading the second stage

The binary downloaded from the cloud is a ZIP file containing the next stage payload, which is a Delphi DLL executed by a non-malicious binary.

Example of Files downloaded from the cloud.
Files downloaded from the cloud.

The file executed by the malware is a non-malicious executable with a valid signature (“Securityo6Z3.exe”).

Screenshot of certificate found in the file executed by the malware.
Certificate found in the file executed by the malware.

The malicious DLL is then loaded by the non-malicious binary through a DLL search order hijacking vulnerability, the same technique that is used by some of the downloaders.

Example of non-malicious binary loading the next stage DLL.
Non-malicious binary loading the next stage DLL.

Second stage

The second stage is a Delphi malware responsible for decrypting and loading Ousaban’s payload in the following flow:

  1. Loads the encrypted bytes of Ousaban from disk;
  2. Decrypts Ousaban payload using a key stored in the “.data” section;
  3. Decrypts the code that runs Ousaban using the same key, stored in the “.data” section.
Example of decryption key and encrypted code stored in the “.data” section of the second stage
Decryption key and encrypted code stored in the “.data” section of the second stage.

The encrypted payload of Ousaban is located among the files downloaded from the cloud, named “ZapfDingbats.pdf”.

Example of third stage encrypted among files downloaded from the cloud.
Third stage encrypted among files downloaded from the cloud.

Once running, the second stage loads Ousaban’s encrypted bytes, which will be decrypted using the key stored in the PE “.data” section.

Screenshot of encrypted Ousaban payload being loaded.
Encrypted Ousaban payload being loaded.

Aside from decrypting the payload, the second stage also decrypts the code that will execute Ousaban in runtime, probably to slow down reverse engineering.

Screenshot of second stage decrypting and loading Ousaban payload.
Second stage decrypting and loading Ousaban payload.

We created a Python script that can be used to statically decrypt Ousaban payloads, using the same algorithm found in the malware. The code can be found in our GitHub repository.

Important API calls used by this stage are also dynamically resolved, another common technique to slow down reverse engineering.

Screenshot of APIs dynamically loaded by the malware.
APIs dynamically loaded by the malware.

Ousaban payload

Ousaban is a Delphi banking trojan, mainly focused on stealing sensitive data from financial institutions in Brazil. As previously mentioned, Ousaban shares many similarities with other Brazilian banking malware, such as the algorithm to decrypt the strings and overlay capabilities.

Ousaban commonly packs/protects its payloads with UPX or Enigma.

Example of Ousaban payload packed with UPX.
Ousaban payload packed with UPX.

One of the most characteristic aspects of Brazilian-sourced banking malware is the algorithm used to encrypt/decrypt important strings.

Screenshot of Ousaban encrypted strings.
Ousaban encrypted strings.

The algorithm used as a base by these trojans was originally demonstrated in a Brazilian magazine called “Mestres Da Espionagem Digital” in 2008. Simply put, it parses the hexadecimal string and uses a chained XOR operation with the key and the previous byte of the string.

Screenshot of part of the algorithm to decrypt the strings, commonly found in Brazilian banking malware.
Part of the algorithm to decrypt the strings, commonly found in Brazilian banking malware.

We created a Python script that can be used to decrypt strings from malware that uses this algorithm, such as Ousaban, Guildma, Grandoreiro, and others. The code can be used to decrypt a single string:

Screenshot of decrypting a single string from the malware.
Decrypting a single string from the malware.

Or to decrypt multiple strings at once, saving the result in a JSON file and also providing the option to show in the console.

Screenshot of decrypting multiple strings from the malware.
Decrypting multiple strings from the malware.

Like other Brazilian-sourced malware, Ousaban monitors the title text from the active window and compares it with a list of strings, to verify if the victim is accessing the website or an application of one of its targets.

Exammple of malware monitoring windows titles.
Malware monitoring windows titles.

In the files we analyzed, we found Ousaban targeting over 50 different financial institutions. If the window title matches one of the targets, Ousaban starts the communication with the C2 address, providing the option to the attacker to access the machine remotely.

C2 communication

Ousaban stores the C2 address remotely. In this case, the malware is using Pastebin to fetch the data. In 2021, this malware was also spotted using Google Docs to fetch this information.

Within the files downloaded from the cloud by the first stage, there’s a file named “Host”, which stores the external location of the C2 configuration. The information is encrypted with the same algorithm used in the strings.

Example of C2 configuration stored on Pastebin.
C2 configuration stored on Pastebin.

The data is stored in a dictionary, where the C2 host is also encrypted with the same algorithm used in the strings.

""
Retrieving and decrypting the C2 server address.

Ousaban only starts the communication once a targeted company is identified.

Screenshot of Ousaban C2 communication.
Ousaban C2 communication.

Lastly, the Ousaban samples we analyzed contain a routine to communicate via Telegram using Webhooks, likely to be used as a secondary channel.

Screenshot of part of Ousaban code to communicate via Telegram.
Part of Ousaban code to communicate via Telegram.

Conclusão

Ousaban is a malware designed to steal sensitive information from several financial institutions, mainly based in Brazil. Ousaban shares many similarities with other Brazilian-based banking trojans, such as Guildma and Grandoreiro. Also, as we demonstrated in this analysis, the attackers behind this threat are abusing multiple cloud services throughout the attack chain. We believe that the use of the cloud will continue to grow among attackers especially due to cost and ease.

Proteção

O Netskope Threat Labs está monitorando ativamente esta campanha e garantiu cobertura para todos os indicadores de ameaças e cargas conhecidas. 

  • Proteção Contra Ameaças Netskope
    • Win32.Malware.Heuristic
    • Win32.Infostealer.Heuristic
  • A Netskope Advanced Protection oferece cobertura proativa contra essa ameaça.
    • Gen.Malware.Detect.By.StHeur indica uma amostra que foi detectada usando análise estática
    • Gen.Malware.Detect.By.Sandbox indica uma amostra que foi detectada por nosso sandbox na nuvem

IOCs

All the IOCs related to this campaign and scripts can be found in our GitHub repository.

author image
Gustavo Palazolo
Gustavo Palazolo é especialista em análise de malware, engenharia reversa e pesquisa de segurança, atuando há muitos anos em projetos relacionados à proteção contra fraudes eletrônicas. Atualmente, ele está trabalhando na Equipe de Pesquisa da Netskope, descobrindo e analisando novas ameaças de malware.

Stay informed!

Subscribe for the latest from the Netskope Blog