Description

Cybersecurity experts have uncovered a new version of the ZLoader malware, version 2.9.4.0, which utilizes a Domain Name System (DNS) tunneling protocol for command-and-control (C2) communications. This update demonstrates ongoing efforts by cybercriminals to refine the malware’s functionality following its reappearance in September 2023, nearly two years after its original infrastructure was disrupted. Zscaler ThreatLabz reports that the latest iteration features a custom DNS tunneling protocol for C2 interactions, along with an interactive shell supporting over a dozen commands. These capabilities could facilitate ransomware operations, making the malware more robust against detection and containment efforts. Known by aliases such as Terdot, DELoader, or Silent Night, ZLoader serves as a malware loader designed to deliver additional malicious payloads. Recent campaigns have associated it with the Black Basta ransomware group, with attackers exploiting remote desktop connections under the pretense of tech support to distribute the malware. The infection chain begins with a payload named GhostSocks, which subsequently deploys ZLoader. The updated ZLoader includes advanced anti-analysis techniques, a domain generation algorithm (DGA), and safeguards to prevent execution on unintended targets. While HTTPS POST requests remain its primary channel for C2 communication, the addition of DNS tunneling enables encrypted data transfers through DNS packets, complicating detection. These updates highlight ZLoader’s growing significance as a tool in ransomware operations.