In a significant cybersecurity development, researchers from Morphisec have uncovered a sophisticated malware strain named ResolverRAT that is specifically targeting healthcare and pharmaceutical sectors. The new malware is designed to steal sensitive data and employ advanced evasion methods that make traditional detection techniques largely ineffective. ResolverRAT spreads through phishing emails, often written in localized languages and leveraging legal or regulatory lures to increase its chances of success. The malware’s complex design and its ability to bypass common security measures make it a formidable threat for organizations in critical industries.
Key Insights into
ResolverRAT operates through a series of multi-layered techniques aimed at evading detection while stealing valuable data. Its attack chain begins with phishing emails, which serve as the initial entry point. These emails often use carefully crafted lures related to legal issues, such as investigations or copyright violations, to convince recipients to open the attached malicious files. Once downloaded, the malware is triggered and begins its sophisticated exploitation process.
The malware is classified as a remote access trojan (RAT), and it takes advantage of advanced in-memory execution. This means that it does not leave static files on the infected machine, making it much harder to detect using traditional file-based scanning tools. Additionally, it employs dynamic resource handling techniques at runtime, which complicates both static and behavioral analysis. The name “ResolverRAT” stems from its reliance on these runtime resolution mechanisms.
Discovered in March 2025, the malware shares similarities with previous campaigns such as Rhadamanthys and Lumma RAT, although Morphisec researchers have labeled it as a distinct malware family. These overlapping traits suggest that the malware is likely connected to threat actor infrastructure used in earlier attacks.
One of the key delivery mechanisms for the malware is DLL side-loading, where the malicious payload is executed through a legitimate file—hpreader.exe. This tactic mirrors methods used in past Rhadamanthys malware campaigns, pointing to the possibility of a shared toolkit or coordinated activity between different threat actors.
The malware operates in multiple stages, starting with a loader that decrypts and executes the malicious payload. The payload itself is AES-256 encrypted and compressed, with obfuscated keys, further hindering analysis. Once decrypted, the malware runs entirely in memory, preventing static analysis from identifying its malicious behavior. It also uses a variety of evasion techniques, such as string obfuscation, to thwart detection tools.
To maintain persistence, ResolverRAT creates registry entries and files in various directories, including AppData, Program Files, and User Startup folders. This ensures that even if part of the malware’s persistence mechanisms are thwarted, other components will continue running, making it resilient to detection and removal.
What Undercode Says:
ResolverRAT exemplifies the growing sophistication of modern malware campaigns, particularly those targeting critical sectors like healthcare and pharmaceuticals. Its use of advanced in-memory execution and evasion tactics signals an evolution in cybercriminal methodology. This move towards leveraging dynamic resource resolution and API manipulation further underscores the malware’s ability to circumvent detection by conventional security tools. Unlike previous threats, which focused on static file-based signatures, ResolverRAT operates with a near invisibility factor that makes it highly challenging for even the most advanced antivirus solutions to catch.
The multi-stage infection process and use of AES encryption for payload delivery further amplify the risk posed by ResolverRAT. By executing its code entirely in memory and using obfuscation techniques, it significantly reduces the likelihood of detection. Moreover, its persistence mechanisms ensure it can survive attempts to remove it, increasing its operational lifespan on compromised systems.
ResolverRAT’s multi-country targeting, evidenced by phishing emails in native languages, suggests that the attackers are running a global campaign aimed at spreading the malware across various regions. The legal lures used in the phishing emails also highlight a growing trend in which attackers tailor their messages to the specific cultural and regulatory contexts of their targets. This highly localized approach not only increases the likelihood of success but also makes it harder to attribute the attack to specific threat actors.
Given the complexity of the malware’s command-and-control (C2) infrastructure, which uses IP rotation and custom protocols, it becomes clear that this is not a typical ransomware or opportunistic attack. Rather, the malware is designed to operate with high resilience and a focus on long-term data exfiltration. The use of certificate-based authentication and SSL inspection bypass further enhances its stealthiness, as it can maintain a private validation chain between the implant and the C2 server.
For healthcare organizations and pharmaceutical firms, this represents a significant threat. The potential for data theft is enormous, considering the value of sensitive patient and drug-related information. Moreover, ResolverRAT’s ability to evade detection while maintaining a foothold in compromised systems underscores the importance of using advanced behavioral analysis tools in tandem with traditional signature-based detection methods.
Fact Checker Results:
- Local Phishing Tactics: The targeted use of local languages and legal lures aligns with the latest trends in global malware campaigns.
- Stealthy Execution: ResolverRAT’s reliance on in-memory execution and runtime resource resolution makes it difficult to detect by traditional means, a fact corroborated by Morphisec’s findings.
- Targeted Sectors: The focus on healthcare and pharmaceutical industries underscores the increased targeting of sectors with high-value sensitive data.
References:
Reported By: securityaffairs.com
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