GootLoader (Dropper) – Malware

Overview

Gootloader is a notable strain of malware that has gained prominence for its sophisticated approach to delivering secondary payloads and executing malicious activities. First emerging in the cybersecurity landscape as a relatively straightforward JScript-based threat, Gootloader has significantly evolved over the years, particularly since 2022. This malware has become a common vector for other malicious tools and ransomware, such as Cobalt Strike and Sodinokibi, making it a significant concern for enterprises and cybersecurity professionals alike. At its core, Gootloader operates by exploiting search engine optimization (SEO) tactics and compromised websites to lure victims into downloading a seemingly benign ZIP archive. This archive is crafted to appear as a document that the user has actively sought, such as a contract or financial agreement, thereby increasing the likelihood of execution. Once the ZIP file is opened, it unleashes a JScript payload that initiates a complex execution flow designed to evade detection and deploy additional malicious software.

Targets

• Individuals
• Finance and Insurance
• Public Administration
• Manufacturing

How they operate

Upon execution, Gootloader performs an initial check to determine if the affected system is connected to an Active Directory domain. This step is crucial as it helps the malware tailor its subsequent actions based on the system environment. If the system is part of a domain, Gootloader may deploy more advanced payloads, such as Cobalt Strike, Gootkit, Osiris, or Sodinokibi ransomware. The malware utilizes a combination of JScript and PowerShell commands to carry out its operations, which helps it maintain persistence and evade detection. Gootloader’s infection process involves multiple stages, each designed to bypass security measures and maintain access to the compromised system. Initially, the malware leverages Windows Script Host (WSH) components like wscript.exe and cscript.exe to execute its JScript payloads. In recent updates, Gootloader’s operators have altered their approach, incorporating different Windows Registry keys for storage and modifying process hierarchies. This evolution includes using alternative execution methods and incorporating PowerShell to execute commands via a standard input (StdIn) stream, which reduces the visibility of its activities. The malware’s detection and removal can be challenging due to its use of various techniques to hide its presence and evade security mechanisms. Gootloader often creates and maintains malicious scheduled tasks and registry entries to ensure persistence. For effective remediation, security professionals must identify and halt malicious instances of wscript.exe, cscript.exe, and powershell.exe, as well as remove any related scheduled tasks and registry keys. The malware’s ability to adapt and employ sophisticated methods underscores the need for robust detection strategies and continuous monitoring to mitigate its impact.

MITRE Tactics and Techniques

Initial Access

T1566: Phishing Gootloader’s initial infection vector is often through phishing. The malware operators use SEO poisoning to lead victims to download a ZIP archive disguised as a legitimate document, such as a contract or financial agreement.

Execution

T1059: Command and Scripting Interpreter Gootloader heavily relies on scripting languages to execute its payloads. It uses JScript files executed by wscript.exe and cscript.exe, as well as PowerShell scripts, to carry out its operations.

Persistence

T1547: Boot or Logon Autostart Execution Gootloader may establish persistence by creating malicious scheduled tasks or modifying registry keys to ensure that it remains active on the system after a reboot or logon.

Privilege Escalation

T1068: Exploitation for Privilege Escalation While not always directly associated with Gootloader, the malware’s later stages might exploit vulnerabilities to escalate privileges if the initial infection does not have the necessary permissions.

Defense Evasion

T1027: Obfuscated Files or Information Gootloader employs obfuscation techniques to hide its malicious JScript files and PowerShell commands, making it harder for traditional security tools to detect its presence.

Credential Access

T1003: Credential Dumping Although not a primary function, some payloads delivered by Gootloader, like Cobalt Strike or Gootkit, might include capabilities to dump credentials from the compromised system.

Discovery

T1083: File and Directory Discovery The malware might use discovery techniques to enumerate files and directories to identify valuable targets or areas of interest on the compromised system.

Lateral Movement

T1021: Remote Services Gootloader itself may not perform lateral movement directly but can deploy payloads like Cobalt Strike that use remote services for lateral movement within a network.

Command and Control

T1071: Application Layer Protocol Gootloader’s payloads might use application layer protocols (e.g., HTTP/HTTPS) to communicate with their command and control (C2) servers.

Impact

T1486: Data Encrypted for Impact If Gootloader deploys ransomware such as Sodinokibi, it can encrypt data to disrupt the organization and demand a ransom.

References:

• What Is GootLoader Malware?
• Gootloader