Venomous warfare: Metasploit’s Lethal Arsenal Unleashed in a hard-hitting shellcode

EXECUTIVE SUMMARY

• The malware employs sophisticated evasion techniques and multiple layers of obfuscation to conceal its true nature.
• Initial examination reveals encoded PowerShell commands, which, upon decoding, unveil a multi-stage payload deployment process.
• Further analysis exposes the configuration of Metasploit parameters within the shellcode, indicating the strategic selection of port 4444 for remote access.
• The malware leverages Windows APIs such as `WSAAccept`, `VirtualAlloc`, and `recv` to establish and execute malicious connections, showcasing advanced capabilities.
• Notably, the absence of explicit IP addresses in the shellcode suggests adaptability to various network environments.
• The complexity of this malware underscores the significance of employing comprehensive analysis techniques to identify and mitigate evolving cyber threats.

INTRODUCTION

The “HEXSH3LL” shellcode was obtained in response to an incident involving the compromise of an international bank by a particular strain of malware. During the investigation, incident responders and forensic analysts discovered this shellcode embedded within a registry key. Remarkably, this registry key was leveraged to schedule a recurring task, prompting the execution of the shellcode every hour. This sophisticated deployment method underscores the strategic and persistent nature of the attack, highlighting the need for rigorous cybersecurity measures to detect and mitigate such threats effectively.

MALWARE DETAILS

METADATA

FUNCTIONALITY

OVERVIEW

The examined malware exemplifies a sophisticated cyber threat, distinguished by its employment of intricate evasion strategies and multi-faceted obfuscation methodologies. Initial analysis reveals the presence of encoded PowerShell commands, indicative of a nuanced multi-stage deployment process. Upon decoding, these commands unveil a series of meticulously orchestrated actions, underscoring the malware’s complexity and strategic intent.

 Moreover, a deeper examination uncovers the meticulous configuration of Metasploit parameters within the shellcode, with particular emphasis on the strategic selection of port 4444 for remote access capabilities. This deliberate choice speaks to the malware’s adaptability and underscores its sophistication in leveraging established network protocols for malicious activities. Furthermore, the malware demonstrates a keen reliance on Windows APIs, notably `WSAAccept`, `VirtualAlloc`, and `recv`, to establish and execute malicious connections. Notably, the absence of explicit IP addresses within the shellcode hints at the malware’s versatility, allowing it to seamlessly adapt to diverse network environments.

Such observations underscore the imperative for rigorous and comprehensive analysis methodologies in effectively identifying and mitigating the ever-evolving landscape of cyber threats.

TECHNICAL ANALYSIS

Following this stage, an in-depth technical examination will commence to dissect the acquired malware, unveiling its underlying attributes and operational intricacies. This analytical endeavor will entail a thorough scrutiny of the malware’s code structure, behavior, and propagation mechanisms. Utilizing advanced forensic tools and methodologies, cybersecurity professionals will dissect the malware’s execution flow, detect any obfuscation techniques deployed to evade detection, and evaluate its potential impact on compromised systems. Furthermore, dynamic analysis methods will be employed to execute the malware within controlled environments, allowing for real-time monitoring of its activities and interactions with system resources. Additionally, static analysis will delve into the malware’s binary code and embedded components, uncovering concealed functionalities or indicators of compromise. Through this systematic and comprehensive investigation, valuable insights will be derived to inform mitigation strategies, enrich threat intelligence, and bolster defenses against similar cyber threats in the future.

The command line string `%COMSPEC% /b /c start /b /min powershell.exe` presents a subtle yet potentially impactful method of executing PowerShell commands without arousing suspicion. This technique is of particular interest in security contexts where clandestine operations are paramount. Breaking down the components of the command reveals a sophisticated approach to evading detection. Initially, `%COMSPEC%` leverages environment variables to access the system’s command interpreter, typically `cmd.exe`. The subsequent use of `/b` and `/c` ensures that the command executes without spawning a visible command prompt window, thus concealing its presence from the user. With the introduction of the `start` command, a separate execution environment is initiated, further obscuring the operation’s visibility. The inclusion of `/b` and `/min` directives within `start` orchestrates the execution of PowerShell in a minimized window, minimizing its footprint on the desktop.

 Ultimately, the invocation of `powershell.exe` enables the execution of PowerShell commands discreetly, offering a covert avenue for malicious actors to exploit system vulnerabilities without drawing attention. Understanding and mitigating such techniques is crucial in fortifying defenses against clandestine activities and safeguarding system integrity.

The discovery of decoded PowerShell code reveals a multi-layered obfuscation tactic employed to conceal malicious activities. Upon inspection, it was revealed that the code contains another base64-encoded command, indicative of a sophisticated evasion strategy. Notably, the presence of `IO.Compression.GzipStream` points to the compression of data using the Gzip algorithm. This compression technique is commonly utilized to reduce file size and is now evidently employed to obscure the true nature of the payload. Unraveling these layers of obfuscation underscores the adversary’s commitment to circumventing detection mechanisms. It is imperative for security practitioners to possess the capability to decipher such intricacies to effectively thwart potential threats. By employing advanced analysis techniques and remaining vigilant against evolving tactics, organizations can fortify their defenses and mitigate the risks posed by covertly executed PowerShell commands.

In the meticulous analysis of encoded PowerShell commands, cybersecurity researchers recently uncovered a sophisticated evasion tactic involving the Gunzip algorithm. Upon decryption using CyberChef, the concealed payload revealed yet another layer of obfuscation: a base64-encoded script. This revelation underscores the adversaries’ commitment to employing multi-faceted techniques to elude detection mechanisms.

Further examination of the decoded base64 script uncovered a binary file, intriguingly commencing with “FC” bytes, a hallmark characteristic of shellcode. This discovery highlights the ingenuity and complexity of modern cyber threats, necessitating a proactive approach to defense. As organizations strive to bolster their cybersecurity posture, understanding and countering such intricate evasion tactics becomes paramount. 

Through meticulous examination using a hex editor, the analyst discerned the presence of a shellcode characterized by its initial byte “FC,” a widely recognized identifier for such malicious payloads. This discovery underscores the expertise and attention to detail required in the forensic analysis of malware artifacts. By identifying and interpreting these telltale signatures, cybersecurity professionals can effectively pinpoint and assess the nature of potential threats, enabling informed decision-making in threat mitigation efforts.

SHELLCODE ANALYSIS USING IDA-PRO DISASSEMBLER

Introduction to IDA-Pro

The IDA-Pro Disassembler, created by Hex-Rays, is a fundamental tool in the field of reverse engineering and malware analysis. Renowned for its strength and adaptability, IDA-Pro is highly valued by cybersecurity experts globally for its ability to disassemble and scrutinize binary executables with exceptional accuracy.

At its core, IDA-Pro utilizes advanced algorithms to decompile binary executables into human-readable assembly code, empowering analysts to understand the inner workings of software, firmware, and malware. Its user-friendly interface and extensive feature set enable analysts to navigate through intricate code structures, identify critical functions, and uncover potential vulnerabilities or malicious behavior.

IMPORTING IDA-PYTHON SCRIPT TO RESOLVE API HASHES

The analyst seamlessly integrated a Python script into the disassembler to decode and resolve the hashes associated with Windows API functions. This strategic approach facilitated the transformation of opaque API calls into human-readable format, enhancing the understanding of the malware’s functionality. Notably, key WINAPIs such as `WSAAccept`, `VirtualAlloc`, and `recv` were among those scrutinized, shedding light on critical aspects of the malware’s behavior. By leveraging this methodical analysis, cybersecurity experts gained valuable insights into the malware’s capabilities and potential impact on compromised systems, ultimately informing targeted mitigation strategies and defense measures against similar threats.

In the ongoing effort to dissect and understand the inner workings of a malware sample, cybersecurity analysts have imported a Python script into IDA, a renowned disassembler and debugger tool. This strategic move aims to convert the obfuscated API calls, hashed using WINAPIs, into human-readable format, thus unraveling critical insights into the malware’s functionality. By leveraging IDA’s robust capabilities for reverse engineering, analysts can systematically decode and analyze the malware’s behavior, shedding light on its operational objectives and potential impact. This meticulous process underscores the importance of utilizing advanced tools and methodologies to dissect complex malware specimens, enabling defenders to enhance their threat intelligence and fortify their defenses against evolving cyber threats.

Within the intricate landscape of malware analysis, a pivotal discovery emerged as analysts encountered a veil of data garbage obscuring the code’s true nature. Employing a strategic combination of actions within IDA, specifically selecting all and pressing “U” in the keyboard to undefine followed by “C” to reveal, uncovered the obfuscated code. This revealed a previously concealed function called at the outset of execution. Such breakthroughs illustrate the meticulous and iterative nature of cybersecurity research, where uncovering obscured elements often unveils critical insights into a malware’s operation. By harnessing the capabilities of advanced tools like IDA, analysts can systematically dismantle layers of obfuscation, empowering defenders to glean actionable intelligence and proactively strengthen their security posture against emerging threats.

Navigate to the “Files” option within IDA Pro,and select “script file” from the dropdown menu. Subsequently, choose the desired Python script responsible for resolving the hashes associated with the malware sample. Upon selection, the script seamlessly integrates into the IDA Pro environment, facilitating the resolution of obscured API calls and providing valuable insights into the malware’s functionality. This streamlined process exemplifies the sophisticated tools and methodologies employed in contemporary malware analysis, enabling cybersecurity practitioners to decipher complex code structures and enhance their understanding of potential threats.

Delving into the intricacies of the “sub_88” function within the malware’s code reveals a pivotal discovery, leading to an expansive section dedicated to configuring the parameters for the entire payload generated by msfvenom. This revelation marks a significant milestone in the analysis process, shedding light on the detailed orchestration of the malicious payload’s construction. The meticulous examination of this function unveils critical insights into the attacker’s intentions, providing cybersecurity researchers with valuable intelligence to assess the scope and sophistication of the threat. Such findings underscore the importance of comprehensive analysis techniques in uncovering the inner workings of malware and arming defenders with the knowledge needed to effectively mitigate risks and safeguard systems against exploitation.

Within the examined code, a significant discovery surfaces in the form of a WINAPI function labeled “bind.” This API holds considerable importance in the realm of malware payloads, serving as a cornerstone for establishing a secure and persistent connection between the threat actor and the compromised system. The utilization of “bind” underscores the malicious actor’s intent to maintain control and facilitate communication channels for subsequent malicious activities. Such findings are instrumental in understanding the tactics and techniques employed by adversaries, enabling cybersecurity practitioners to devise effective countermeasures and fortify defenses against intrusions and data exfiltration attempts.

During the analysis of the shellcode, a significant observation was made concerning the absence of explicit mentions of IP addresses within the “bind” function. Instead, the focus remained solely on identifying the listening port number. This detail suggests a strategic decision by the threat actor, possibly indicating a preference for flexibility and adaptability in deploying the malware. By abstracting the specification of IP addresses, the malware exhibits the ability to adapt to various network environments, potentially enhancing its effectiveness and evading detection mechanisms. This finding underscores the dynamic nature of contemporary cyber threats and underscores the importance of thorough analysis in identifying subtle nuances that may have implications for mitigating threats effectively.

Port 4444 is widely recognized as a default listening port in the Metasploit framework, favored by threat actors for its versatility in enabling remote access and control over compromised systems. The prominence of this port in the observed shellcode suggests a deliberate choice by the threat actor, likely aiming to leverage a familiar and widely utilized infrastructure for malicious purposes. By employing this default port, the malware adheres to established practices in the cybersecurity landscape, simplifying communication protocols and potentially exploiting vulnerabilities commonly associated with this port configuration. This underscores the importance of comprehending adversary tactics and patterns, empowering defenders to proactively anticipate and address emerging threats.

The `WSAAccept` WINAPI serves as the initial step in the malware’s operation, facilitating the acceptance of incoming connections. Once data, often containing the malicious shellcode, is received, the malware proceeds to allocate memory for the shellcode’s execution using the `VirtualAlloc` WINAPI. This critical allocation ensures that the shellcode has dedicated memory space to function. Following this, the final phase involves the execution of the shellcode via the `recv` WINAPI, enabling the malware to execute its intended payload on the compromised system. This meticulously orchestrated process highlights the malware’s sophisticated design, showcasing its strategic use of Windows APIs to achieve its malicious goals. Understanding these intricacies is vital for cybersecurity professionals to effectively detect, analyze, and counter such threats.

DYNAMIC ANALYSIS OF THE SHELLCODE

To glean further insights from the shellcode, the analyst opted to utilize “scbdbg,” also known as the Shellcode Debugger. This strategic choice was aimed at delving deeper into the behavior and structure of the shellcode, with the goal of uncovering additional clues that could enhance understanding of the malware’s complexities. By leveraging specialized debugging tools like “scbdbg”, cybersecurity professionals can meticulously observe the execution of the shellcode, examining memory accesses, function calls, and other dynamic behaviors. This meticulous examination serves as a pivotal step in the investigative process, enabling analysts to uncover concealed functionalities, bypass obfuscation techniques, and extract valuable intelligence to inform mitigation strategies.

The analyst’s examination yielded minimal results, only managing to identify the Windows API functions employed within the shellcode. Despite thorough investigation, further insights into the shellcode’s behavior or objectives remained elusive. This underscores the inherent challenges of analyzing intricate malware and emphasizes the necessity of employing diverse investigative methods. While discovering the used WINAPIs offers valuable context, it underscores the ongoing need for persistent exploration to fully understand the malware’s capabilities and intentions.

CONVERTING THE SHELLCODE INTO AN EXECUTABLE

The analyst then transformed the shellcode into a portable executable (PE) file to observe potential changes in behavior. This approach aimed to uncover differences in how the shellcode functions when executed in a different format. By converting it into a PE file, the analyst sought deeper insights into its capabilities and impact on compromised systems. This methodical analysis allows cybersecurity professionals to better understand the nuances of the malware’s operation and develop more effective mitigation strategies.

Following execution, the portable executable file was successfully generated.

ANALYSIS THROUGH EXECUTION OF THE PORTABLE EXECUTABLE FILE

When running the PE file through Process Monitor (Procmon), a key aspect of the analysis involves capturing process names while applying specific filters, particularly focusing on network-related DLLs and registry hives associated with network connections. This targeted approach allows cybersecurity analysts to gain insights into the behavior of the executed process in relation to network communication. Through careful monitoring, Procmon provides visibility into processes interacting with network resources, facilitating the detection of potentially malicious activities such as unauthorized data exfiltration or command-and-control communication. This proactive approach aligns with established best practices in malware analysis, highlighting the importance of utilizing advanced monitoring tools to effectively detect and counter emerging threats.

CONCLUSION

Understanding the utilization of Powershell wrappers and initial shellcode loaders is paramount, as they often serve as pivotal components in sophisticated attack scenarios. By delving into the inner workings of shellcode, one gains the ability to automate detection and response mechanisms effectively. This knowledge can seamlessly integrate into broader digital forensics, incident response, and Security Operations Center (SOC) workflows, enhancing overall security posture. Moreover, automated extraction of Indicators of Compromise (IOCs) becomes feasible, even in offline environments, on-premises infrastructures, and under non-disclosure agreement (NDA) constraints. This holistic approach empowers organizations to proactively identify and mitigate threats, bolstering resilience against evolving cyber threats.

~ Author : Nathaneal Meththananda ~