Cybersecurity researchers have recently disclosed the emergence of a new variant of QakBot malware that features an enhanced BackConnect (BC) module. The BC module, commonly used by threat actors to maintain persistence and perform various malicious tasks, enables remote access to compromised systems. Walmart’s Cyber Intelligence team identified two versions of the BC module, named DarkVNC and KeyHole, both of which allow threat actors to control infected systems and gather crucial system information. The malware was discovered on the same infrastructure previously used to distribute ZLoader, another malware loader recently updated to incorporate DNS tunneling for command-and-control communications.
Originally designed as a banking trojan, QakBot has evolved into a potent malware loader capable of delivering subsequent payloads such as ransomware. Its ability to use the BC module to facilitate remote access and proxy operations makes it a dangerous tool in the hands of cybercriminals. The latest analysis revealed that the BC module has been upgraded to function autonomously, collecting system information to aid in follow-up exploitation without direct intervention from the attacker. Walmart emphasized that the BC module not only provides a means for remote control but also significantly enhances the malware’s ability to remain undetected.
In an independent analysis by Sophos, the new BC malware was attributed to a threat cluster tracked as STAC5777, which overlaps with the notorious Storm-1811 cybercriminal group.
This group is known for leveraging Microsoft Teams and Quick Assist to gain remote access to victims’ systems, tricking them into granting access via social engineering tactics. These tactics often involve email bombing and vishing (voice phishing) to convince users to allow attackers to install backdoors or ransomware. Sophos also noted that the attackers operated their own Microsoft Office 365 service tenants to launch these attacks, exploiting the default configurations that allow external users to initiate chats or meetings with internal users.
The interconnected nature of the cybercrime ecosystem became evident with the discovery that Black Basta ransomware operators, who previously relied on QakBot for deployment, are now distributing ZLoader as well. The emergence of the new BC module further strengthens the possibility that the QakBot developers are collaborating with or supporting other cybercriminal groups, including Black Basta. This interconnected environment allows malware developers to continuously evolve and enhance their tools, making it increasingly difficult for cybersecurity defenses to keep up with the rapidly changing threat landscape.
