A sophisticated new threat campaign targeting Windows systems has now emerged, leveraging a new strain of malware called winos 4.0. This attack, which has been active since January 2025, compromises organizations across the island nation of Taiwan. It demonstrates the evolving tactics of cybercriminals who employ social engineering techniques combined with advanced malware deployment strategies. The threat actors behind this campaign have shown remarkable persistence and sophistication in their approach, utilizing very convincing phishing emails. These deceptive messages masquerade as official communications from Taiwan’s National Taxation Bureau and are designed to trick their many unsuspecting recipients. This carefully planned operation highlights a significant and growing threat to corporate networks located in the East Asian region.
The attack chain begins with carefully crafted phishing emails that appear to originate from legitimate government agencies or business partners. These messages typically focus on urgent topics such as tax notifications, various pension updates, or invoice processing to create a sense. This creates a sense of immediacy that compels recipients to interact with the malicious content that has been sent to them. The emails often contain PDF attachments or HTML files that redirect users to download pages hosting the winos 4.0 payload. This payload is often packaged within password-protected ZIP files to evade detection by automated security scanners, a common evasion tactic. The impact of this campaign extends far beyond individual system compromise, as the malware is designed to collect sensitive information.
The winos 4.0 malware demonstrates sophisticated persistence tactics that enable it to maintain long-term access to all compromised systems.
These techniques allow it to evade detection by security software while it is exfiltrating data from the infected computer systems. Once executed, the malware performs several critical operations to establish its presence within the target environment for the attackers. The initial payload, which is distributed through the dokan2.dll component, creates a dedicated thread responsible for decrypting and executing shellcode. A particularly noteworthy aspect of the malware’s persistence strategy involves its clever manipulation of various different system DLL files. The malware establishes registry-based persistence by creating an infection marker.
To achieve the highest privilege levels on a compromised system, winos 4.0 implements a multi-stage privilege escalation process.
The malware first enables the SeDebugPrivilege to bypass the standard WinLogon access restrictions, a common technique used by attackers. It then utilizes the ImpersonateLoggedOnUser function to assume SYSTEM level privileges, which grants it significant control over the machine. Finally, the malware impersonates the TrustedInstaller service thread to obtain the maximum possible system control for its various malicious operations. This complex privilege escalation chain clearly showcases the advanced capabilities of the sophisticated threat actors who are behind this new and dangerous malware campaign. They have invested significant resources into developing these methods.