Kaspersky Unmasks Android Banking Trojan Zanubis

Kaspersky experts have analyzed a recent campaign by Zanubis, a banking Trojan distinguished by its adeptness at assuming the guise of legitimate applications. The investigation also sheds light on the AsymCrypt cryptor/loader and the evolving Lumma stealer, underscoring the increasing need for enhanced digital security.

Zanubis, an Android banking trojan, surfaced in August 2022, targeting financial and crypto users in Peru. Impersonating legitimate Peruvian Android apps, it tricks users into granting Accessibility permissions, surrendering control. In April 2023, Zanubis evolved, posing as the official app for the Peruvian governmental organization SUNAT (Superintendencia Nacional de Aduanas y de Administración Tributaria), showcasing increased sophistication. Zanubis is obfuscated with the help of Obfuscapk, a popular obfuscator for Android APK files. Once it gets permission to access the device, it tricks a victim by loading a real SUNAT website using WebView, making it seem legitimate.

It uses WebSockets and a library called Socket.IO to communicate with its controlling server. This allows it to adapt and stay connected even if there are issues. Zanubis doesn’t have a fixed list of target apps unlike other malware. Instead, it can be programmed remotely to steal data when specific apps are running. This malware even creates a second connection, which could give the bad actors full control over your device. And the worst part is, it can disable your device by pretending to be an Android update.

Another recent discovery made by Kaspersky is AsymCrypt cryptor/loader, which targets crypto wallets and is being sold on underground forums. As the investigation showed, it is an evolved DoubleFinger loader version, acting as a “front” to a TOR network service. Buyers customize injection methods, target processes, startup persistence, and stub types for malicious DLLs, concealing the payload in an encrypted blob within a .png image uploaded to an image hosting site. Execution decrypts the image, activating the payload in memory.

Kaspersky’s tracking of cyber threats has also led to the Lumma stealer, an evolving malware lineage. Originally known as Arkei, the rebranded Lumma retains 46% of its former attributes. Disguised as a .docx to .pdf converter, its deceptive distribution triggers the malicious payload when uploaded files return with a double extension .pdf.exe. Over time, the main functionality of all the variants has remained the same: stealing cached files, configuration files and logs from crypto wallets. It can do this by acting as a browser plugin, but it also supports the standalone Binance application. Lumma’s evolution includes acquiring system process lists, changing communication URLs, and advancing encryption techniques.

“Cybercriminals are relentless in their pursuit of monetary gain, venturing into the world of cryptocurrencies and even impersonating government institutions to achieve their objectives. The ever-evolving landscape of malware, exemplified by the multifaceted Lumma stealer and the ambitions of Zanubis as a full-fledged banking Trojan, underscores the dynamic nature of these threats. Adapting to this constant transformation in malicious code and cybercriminal tactics poses an ongoing challenge for defense teams. To safeguard against these evolving dangers, organizations must remain vigilant and well-informed. Intelligence reports play a pivotal role in keeping abreast of the latest malicious tools and attacker techniques, empowering us to stay one step ahead in the ongoing battle for digital security,” comments Tatyana Shishkova, a lead security researcher at GReAT.

In order to prevent financially motivated threats, Kaspersky recommends:

  • Set up offline backups that intruders cannot tamper with. Make sure you can quickly access them in an emergency when needed.
  • Install ransomware protection for all endpoints. There is a free Kaspersky Anti-Ransomware Tool for Businessthat shields computers and servers from ransomware and other types of malware, prevent exploits, and is compatible with pre- installed security solutions.
  • To minimize the likelihood that crypto-miners will be launched, use a dedicated security solution such as Kaspersky Endpoint Security for Businesswith application and web control; behavior analysis helps quickly detect malicious activity, while vulnerability and patch manager protects from crypto-miners that exploit vulnerabilities.