Winsage
February 18, 2025
Researchers from Trend Micro's Threat Hunting team have identified a cyberattack campaign by the APT group Earth Preta, targeting government entities in the Asia-Pacific region, including Taiwan, Vietnam, Malaysia, and Thailand. The group uses spear-phishing emails and advanced malware to compromise Windows systems, notably employing the Microsoft Application Virtualization Injector (MAVInject.exe) to inject malicious payloads into legitimate processes. The attack typically begins with a malicious file, IRSetup.exe, which drops both legitimate and malicious files onto the system, often accompanied by a decoy PDF posing as an official document.
Earth Preta utilizes a modified variant of the TONESHELL backdoor malware, sideloaded using OriginLegacyCLI.exe and a malicious DLL, EACore.dll. This malware communicates with a command-and-control server for data exfiltration and remote operations, offering capabilities such as reverse shell access, file deletion, and persistent storage of victim identifiers. The malware adapts its behavior based on the presence of ESET antivirus software, using different techniques for code injection.
Trend Micro attributes this campaign to Earth Preta with medium confidence, noting that the group has compromised over 200 victims since at least 2022, primarily focusing on government entities and using phishing as the initial attack vector.
