Two Recent Campaigns from Brazil and Korea Exploiting Legitimate Cloud Services

The exploitation of cloud services is a flexible weapon in the hands of attackers, so flexible that we uncover new campaigns abusing legitimate apps on a daily basis. Whether threat actors are driven by cybercrime or cyberespionage, they continue to target different audiences in different geographical regions of the world, exploiting different services in different phases of the attack chain (primarily delivery and distribution of malware, but also command and control, alongside the emerging spearphishing campaigns tailored specifically to target cloud accounts).

Two recent examples bring us to Brazil and Korea, where two distinct operations provided additional, unneeded, proofs of how legitimate internet services can be easily adapted for multiple roles and multiple purposes over the course of a malicious operation. 

In May, researchers at HarfangLab in Brazil discovered a malicious campaign delivering a payload named “AllaSenha” (yet another variant of an old acquaintance for users in Latin america: AllaKore, an open source remote access tool). This variant, characterized by an intricate infection chain involving Python scripts and a Delphi-developed loader, is specifically aimed at stealing credentials of Brazilian bank accounts and also leveraging Azure as its command and control (C2) infrastructure. Azure is particularly flexible for the attackers, as it provides multiple tools that can be abused, and not only by opportunistic criminals. For example, in February 2024, researchers at Mandiant discovered a cyberespionage campaign carried out by an Iranian threat actor tracked as UNC1549, exploiting a network of over 125 Azure command-and-control (C2) subdomains.

Nearly at the same time, researchers at AhnLab found out that cybercriminals were quite busy in South Korea, distributing a malware cocktail (remote access Trojans, cryptocurrency miners, malware downloaders, proxy tools, and anti-AV programs) through cracked versions of Microsoft Office (once again a warning to not install unapproved applications on corporate devices). Unsurprisingly, the cracked installer sporting a well-crafted interface, launched in background an obfuscated .NET malware that contacts a Telegram or Mastodon channel to receive a valid download URL from Google Drive or GitHub from where it downloads an obfuscated payload containing the PowerShell command that ultimately, at the end of the complex attack chain, installs the malware strains onto the system.

While these attacks may be in different countries, involve different threat actors, and have different motivations, a common denominator is the exploitation of legitimate services to make the attack more evasive, concealing the malicious traffic inside legitimate sessions directed to trusted applications too often allow listed by organizations, or at least not inspected adequately.

Mitigating the risk of legitimate cloud services exploited for malware distribution or command and control

Azure, Google Drive, and GitHub are among the thousands of cloud services where the Netskope Next Gen SWG can provide adaptive access control, threat protection, and data loss prevention with a granularity that is impossible for any other web security technology. So, in cases where these services or similar cloud storage apps are not needed by the organization, but are exploited by external attackers to deliver a malicious payload or to host the command and control infrastructure, it is possible to configure a policy for preventing potentially dangerous activities (such as “Upload” and “Download”) from the specific service or the entire category where it belongs.

Netskope customers are also protected against malware distributed from the cloud (and the web in general) by Netskope Threat Protection. Netskope Threat Protection scans web and cloud traffic to detect known and unknown threats with a comprehensive set of engines, including signature-based AV, machine learning detectors for executables and Office documents, and sandboxing with patient zero protection. The threat protection capabilities can be further improved through Netskope Cloud Exchange, which provides powerful integrations to leverage investments across users’ security posture through integration with third-party tools, such as threat intelligence feeds, endpoint protection, and email protection technologies.

Finally, Netskope Advanced Analytics provides specific dashboards to assess the risk of rogue cloud instances being exploited to deliver malware or the risk of becoming the target of anomalous communications, with rich details and insights, supporting security teams in the analysis and mitigation/remediation process.

Stay safe!