The Astaroth Trojan used Facebook and YouTube profiles to support its infection chain in a new phishing campaign targeting Brazilian users.

First observed by Cofense, the phishing emails, which were written in Portuguese, masqueraded as one of three items: an invoice, a show ticket or a civil lawsuit notice. In each case, the email messages lured users into opening an .htm file to initiate the infection chain. Users who did so unknowingly downloaded a .ZIP archive that was geofenced to Brazil and contained a malicious .LNK file.

Upon running the .LNK file, the campaign downloaded JavaScript code from a Cloudflare Workers domain. The JavaScript snippet then pulled down multiple elements used to execute a sample of the Astaroth Trojan.

In this campaign, Astaroth used YouTube and Facebook profiles to host and maintain configuration data for its command-and-control (C&C) infrastructure. This information took the form of data contained within posts on a Facebook profile or within profile information for certain YouTube users. Through this technique, the attackers were able to bypass traditional security tools and collect sensitive data, such as financial information and stored passwords.

Astaroth’s Recent Activity

In September 2018, Cofense discovered a resurgence of Astaroth in which the Trojan potentially compromised as many as 8,000 machines in the span of one week. A few months later, Cybereason spotted a new variant of the malware abusing native operating system (OS) processes and exploiting security products to infect users in Brazil.

Then, in July, the Microsoft Defender ATP Research Team spotted a fileless malware campaign dropping Astaroth into memory.

How to Break an Infection Chain Initiated by Phishing

To help defend against infection chains initiated by phishing attacks, security teams should consider adopting a layered approach to email security that incorporates mail scanning, spam monitoring and other security measures. Companies should also practice ahead-of-threat detection to spot potentially malicious domains before they become active in phishing campaigns and other digital attacks.