DarkGate Campaign: From Document to Phishing Script

 Source: From Document to Script: Insides of Darkgate's Campaign (forcepoint.com)

A recent analysis by Forcepoint's X-labs has uncovered a worrying threat vector through which cyber threats can target users, namely through commonly shared documents, namely those in XLSX, PDF, and HTML formats. These are a natural choice for any attacker primarily because of their sheer ubiquity. They represent trustable file formats for the average end user, who typically would open one upon receiving it with no hesitation or second thoughts. However, the research by X-labs has uncovered a phishing campaign called DarkGate, which utilizes a sophisticated attack methodology in which phishing emails containing standard file formats are just the start of a process, which often culminates in remote code execution and the hijacking of user machines. Notably, the campaign's bait of choice to target users are emails that appear to be invoices from 'Intuit QuickBooks', containing a PDF attachment. 

As mentioned earlier, the typical user would click on such trusted file formats with little to no hesitation, and upon doing so, the attack prompts users to install Java to view the invoice, followed by their redirection to a geofenced URL that downloads a malicious Java Archive (JAR) file. This JAR file serves as the initial entry point of the malware into the system since, upon its execution, it carries out several steps to download and run additional payloads. 

Among the JAR file's contents is a class file that uses an obfuscated 'curl.exe' command to download a ZIP file to a user's system. This ZIP file includes an AutoIt script compiled to execute further commands, such as establishing command and control (C2) through its connections to the relevant external servers. Furthermore, the attack heavily uses obfuscation techniques to hide the script's functionality, showcasing its sophistication and the lengths to which it goes to hide its presence and hamper forensics efforts after the fact. 

DarkGate isn't a completely novel attack, as it builds on previous tactics, techniques, and procedures used in previous malware campaigns. This serves as a worrying indicator of organizational collaboration and the evolution of exploitation mechanisms among attackers. Highlighting this is that URLs used in this campaign have historical connections to other known threat actors, such as QakBot. 

Protecting against attacks like DarkGate is a multifaceted process in which organizations' implementation of robust email security measures occupies a pivotal role. Furthermore, educating end users about the dangers present even in trusted file formats is crucial, along with the institution of more technical controls, such as advanced malware detection systems. In this realm, Forcepoint's X-Labs continue to make strides as they continuously monitor and mitigate these threats, providing essential insights and protection for users. 

For more context and insight regarding this threat vector, feel free to visit Forcepoint's Blog.