RedCurl Uses New QWCrypt Ransomware in Hypervisor Attacks

Discover the novel QWCrypt ransomware used by RedCurl in targeted hypervisor attacks. This article details their tactics, including DLL sideloading and LOTL abuse, and explores the group’s evolving cybercriminal activities.

Bitdefender Labs has revealed a shift in the operational tactics of the long-standing cyber threat group known as RedCurl. This group, also known as Earth Kapre or Red Wolf, has historically maintained a low profile, relying heavily on covert data exfiltration. It has now been linked to a novel ransomware campaign, marking a dramatic change in their activities. This new ransomware strain, dubbed QWCrypt, targets hypervisors, effectively crippling infrastructure while maintaining a stealthy presence.

“This new ransomware…is previously undocumented and distinct from known ransomware families,” the report states.

This discovery prompts a reevaluation of RedCurl’s operational model, which has remained largely puzzling since their emergence in 2018. The group’s targeting patterns further complicates their classification.

While telemetry data points to victims primarily in the United States, with additional targets in Germany, Spain, and Mexico, other researchers have reported targets in Russia, a broad geographical scope atypical for state-sponsored actors. The absence of any historical evidence of RedCurl selling stolen data, a common practice in ransomware operations, adds to the mystery.

Living-off-the-Land (LOTL)

The group uses sophisticated techniques, including DLL sideloading and the abuse of Living-off-the-Land (LOTL) strategies, all while avoiding the use of public leak sites, a critical shift from typical ransomware operations.

The initial access vector used by RedCurl in their ransomware deployment remains consistent with their previous campaigns: phishing emails containing IMG files disguised as CV documents. These files, when opened, execute a malicious screensaver file, which in turn loads a malicious DLL. This DLL then downloads the final payload, using encrypted strings and legitimate Windows tools to evade detection. 

Once inside the network, RedCurl employs lateral movement techniques, utilizing WMI and other built-in Windows tools to gather intelligence and escalate access. The group’s use of a modified wmiexec tool, which bypasses SMB connections, and Chisel, a TCP/UDP tunneling tool, highlights their sophisticated approach.

The ransomware deployment itself is highly targeted. RedCurl uses batch files to disable endpoint security and launch the ransomware’s GO executable, rbcw.exe, which encrypts virtual machines using XChaCha20-Poly1305 encryption and excludes network gateways.

The file also includes a hardcoded personal ID for victim identification.  The ransom note, researchers claim, is not original, but rather a compilation of sections from other ransomware groups. Additionally, the absence of a dedicated data leak site further complicates the understanding of RedCurl’s motives.Bitdefender

Bitdefender’s Hypotheses

Bitdefender proposes two potential hypotheses to explain RedCurl’s unconventional behaviour. The first suggests they may operate as “gun-for-hire” cyber mercenaries, explaining their diverse victimology and inconsistent operational patterns.

The second hypothesis posits that RedCurl prioritizes discreet, direct negotiations with victims, avoiding public attention to maintain extended, low-profile operations. This theory is supported by the group’s targeting of hypervisors while maintaining network gateways, suggesting an attempt to limit disruption and confine the attack to IT departments.

In conclusion, Bitdefender recommends a multilayered defense strategy, enhanced detection and response capabilities, and a focus on preventing LOTL attacks to mitigate the risks posed by groups like RedCurl. They also emphasize the importance of data protection, resilience, and advanced threat intelligence.