A new variant of the Orcinius Trojan has been identified, utilizing a technique called VBA Stomping to obscure its infection. This multi-stage Trojan employs cloud services like Dropbox and Google Docs to stay updated and deliver additional payloads. VBA Stomping involves removing the VBA source code from a Microsoft Office document, leaving only a compiled form of the macro code, known as p-code, which can hide the malware’s true intentions from casual inspection.
The Trojan is initially delivered via an Excel spreadsheet named “CALENDARIO AZZORTI.xls,” which masquerades as an Italian calendar with worksheets about different cities’ billing cycles. The file contains a VBA macro that has been modified through VBA Stomping, making it difficult to detect the malicious code. When the document is opened, the macro executes, performing several actions including hiding warnings, creating registry keys for persistence, and monitoring open windows and keystrokes.
During its operation, the macro accesses encoded URLs to download additional malicious payloads, which are linked to known threats such as Remcos, AgentTesla, Neshta, and HTMLDropper. The URLs point to Dropbox and Google Docs for further malicious content delivery. The Trojan also sets up randomized timers for download attempts and maintains persistence on the infected system.
Researchers warn that this Trojan’s use of VBA Stomping and cloud services for its activities represents an evolution in malware techniques, making it more challenging for traditional security measures to detect and mitigate. The combination of these methods increases the risk of misinterpretation, escalation, and broader impact of the malware.
Reference:
