GuLoader Malware

How Does GuLoader Work?

GuLoader is a remote access trojan (RAT), meaning that it relies on trickery and looking benign to gain initial access to a system. Common GuLoader infection vectors include drive-by downloads and phishing campaigns.

GuLoader is also known for its three-stage infection process. In the first stage, it first gains access and achieves persistence via modified registry keys. During stage two, the malware inspects its environment for signs of analysis tools before injecting shellcode into memory. This injection is accomplished via process hollowing, and the shellcode is encrypted and polymorphic, making it more difficult to detect and remediate. The final stage uses the injected shellcode to download and execute the final malicious executable. GuLoader can also download and deploy a wide range of other malware variants, dramatically increasing the potential threat that it poses to an organization.

GuLoader evades detection via a variety of different mechanisms, including the use of encryption, packing, and polymorphic code. Additionally, GuLoader downloads its malicious code from legitimate websites. In fact, the modern version of GuLoader can download encrypted payloads from Google Drive and other cloud storage systems. This encryption makes it possible for the malware to slip past cloud providers’ scanners and increases the effective lifetime of the malware.

How to Protect

GuLoader is an adaptable and highly effective trojan horse that remains under active development after over three years in operation. However, organizations can take steps to protect themselves and their employees against this malware threat. A number of best practices for protecting against GuLoader and similar malware threats include:

• Employee Education: As a trojan malware, GuLoader relies on trickery and camouflage, pretending to be a legitimate file. Training users to identify and avoid phishing scams and drive-by downloads can help to reduce the risk of infection.
• Endpoint Security: GuLoader uses various evasion techniques, but it also engages in several suspicious and malicious behaviors on an infected system. Endpoint security solutions should be able to detect and block a malware infection before it causes significant damage to the organization.
• Email Security: Phishing emails are a primary GuLoader infection mechanism. Email scanners may be able to identify and then block emails carrying the GuLoader malware before they can reach users’ inboxes.
• Web Security: GuLoader is also commonly distributed via drive-by downloads. Web security solutions can identify signs of a malicious website and block suspicious downloads, preventing the trojan malware from making the move to an end user’s systems.