GuLoader

GuLoader is a potent malware that has been causing significant cybersecurity concerns. It operates by infecting systems through suspicious downloads, emails, or websites and then proceeds to exploit the system, often stealing personal information, disrupting operations, or holding data hostage for ransom. In early 2023, a GuLoader sample was encountered which initially had zero VirusTotal detections, indicating its sophisticated stealth capabilities. The malware uses advanced techniques like ciphertext splitting and control flow obfuscation to enhance its elusiveness, making it harder to detect and block. The GuLoader authors have employed various methods to further obfuscate their Command and Control (C2) configuration, adding another layer of complexity to this malicious software. A detailed analysis of the GuLoader sample revealed anti-analysis instructions, demonstrating the lengths the authors went to ensure their malware remains undetected. Additionally, GuLoader has been seen paired with other malware loaders like Remcos, creating more complex attack chains that are challenging to identify and disrupt. Technical analysis of GuLoader has shed light on the process of locating and extracting C2 configurations from various malware families. However, the evolution of the malware's techniques has defeated previous approaches to extracting GuLoader's configuration. This malware is encrypted using the NSIS Crypter, as indicated in the NSIS Script and Extracting GuLoader Shellcode. This encryption provides an additional layer of security, making it even more difficult for cybersecurity professionals to analyze and neutralize the threat posed by GuLoader.