A new variant of the Astaroth Trojan family employed YouTube channels for command-and-control (C&C) functionality in order to evade detection.

Cisco Talos detected a new Astaroth attack campaign targeting users in Brazil. The operation began when a user received an email written in Portuguese that resorted to a car rental service as a lure in order to trick the user into clicking on a link that masqueraded as an overdue invoice. In actuality, that link redirected the user to Google Drive for the purpose of downloading a malicious ZIP file.

The downloaded ZIP file contained a number of malicious Microsoft Windows shortcut (LNK) files that were responsible for initiating the infection process. This step led the campaign to its second stage of infection. At this point, the operation leveraged multiple layers of obfuscation before using LoLBins to advance itself. It then employed evasion checks and anti-analysis processes, steps that included the use of YouTube channels as its primary C&C infrastructure, to deliver Astaroth as its final payload.

A Look Back at Other Astaroth Attacks

Back in February 2019, Cybereason detected a campaign in which the malware disguised itself as JPEG, GIF and extension-less files in order to evade detection and prey upon Brazilian users. A few months later, the Microsoft Defender APT Research Team spotted an operation in which the malware used only system tools to perform a complex attack chain. Then, in September 2019, Cofense witnessed a phishing campaign where the threat relied on both Facebook profiles and YouTube channels to prey upon Brazilians.

Defend Against Evasive Malware

Security professionals can help defend their organizations against evasive malware like Astaroth by training their machine learning (ML) models to spot evasive tactics, specifically by training models to be familiar with all different types of adversarial techniques. At the same time, infosec personnel should use relevance scoring to fine-tune their threat intelligence for the purpose of improving their defenses against evasive campaigns that pose the greatest threat to them.

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