Indirect Command Execution

Indirect Command Execution [T1202]

Information

• Name: Indirect Command Execution

• ID: T1202

• Tactics: TA0005

Introduction

Indirect Command Execution is classified under the MITRE ATT&CK framework as technique T1202. It refers to attackers leveraging trusted, legitimate processes or applications, such as scripting interpreters, command-line utilities, or third-party software, to indirectly execute malicious commands or payloads. This technique helps adversaries evade detection by masking malicious activities within normal system operations or legitimate software behavior.

Deep Dive Into Technique

Indirect Command Execution typically involves the following technical mechanisms and execution methods:

• Trusted System Utilities and Interpreters

  • Attackers commonly exploit trusted Windows system utilities such as PowerShell, cmd.exe, wscript.exe, cscript.exe, rundll32.exe, regsvr32.exe, and mshta.exe.

  • Linux environments may involve bash scripts, cron jobs, python scripts, or legitimate binaries like wget, curl, or systemd services.

• Third-party Application Exploitation

  • Attackers use legitimate third-party applications such as web browsers, office productivity suites (Microsoft Office macros), PDF readers, or scripting frameworks to indirectly execute malicious commands.

  • Office macros or embedded scripts within documents can indirectly execute malicious payloads without directly invoking suspicious binaries.

• Fileless Execution Methods

  • Attackers may execute commands indirectly without writing payloads to disk, leveraging in-memory execution through scripting engines or PowerShell reflective loading.

  • Techniques such as reflective DLL injection or PowerShell's Invoke-Expression cmdlet are commonly used for indirect, stealthy execution.

• Abuse of Legitimate Features

  • Leveraging legitimate features such as Windows Management Instrumentation (WMI), Scheduled Tasks, Windows Services, or COM objects to indirectly execute commands or scripts.

  • Manipulating trusted processes by injecting malicious code into legitimate binaries or scripts.

When this Technique is Usually Used

Indirect Command Execution is frequently utilized in various stages and scenarios of cyber attacks, including:

• Initial Access and Delivery

  • Malicious documents containing macros or embedded scripts that indirectly execute payloads upon opening.

  • Drive-by downloads leveraging legitimate browser functionality or plugins.

• Execution and Persistence

  • Attackers establish persistent access by scheduling indirect command execution through legitimate scheduled tasks, services, or startup scripts.

  • Malicious scripts executed indirectly through legitimate interpreters to evade endpoint detection solutions.

• Privilege Escalation and Lateral Movement

  • Indirect execution via trusted utilities to escalate privileges or move laterally within a network without triggering security alerts.

  • Utilizing WMI or PowerShell remoting to execute commands indirectly on remote endpoints.

• Defense Evasion

  • Masking malicious activities by embedding commands within legitimate scripts or processes to bypass traditional antivirus and endpoint detection tools.

  • Using indirect execution techniques to evade application whitelisting or behavioral monitoring solutions.

How this Technique is Usually Detected

Effective detection of Indirect Command Execution involves multiple layers of monitoring and analysis:

• Process Monitoring and Behavioral Analysis

  • Monitoring and alerting on unusual parent-child process relationships, such as office applications spawning cmd.exe, PowerShell, or scripting engines.

  • Identifying anomalous process execution patterns, including unusual command-line arguments or uncommon script execution.

• Endpoint Detection and Response (EDR) Solutions

  • EDR tools capable of detecting suspicious script execution, command-line parameters, and indirect command invocation through behavioral analytics.

  • Real-time detection of reflective DLL loading, memory-based execution, and suspicious use of scripting interpreters.

• Logging and Auditing

  • Comprehensive logging of PowerShell, WMI, and scripting engine activities (e.g., Script Block Logging, Module Logging).

  • Auditing scheduled tasks, registry modifications, and service creations for indirect command execution indicators.

• Threat Intelligence and IoCs

  • Leveraging known Indicators of Compromise (IoCs) such as suspicious registry keys, scheduled tasks, specific command-line arguments, or known malicious scripts.

  • Utilizing threat intelligence feeds to correlate observed behaviors with known adversary TTPs (Tactics, Techniques, and Procedures).

Specific IoCs include:

• Suspicious PowerShell commands like Invoke-Expression, IEX, DownloadString, or encoded commands (-EncodedCommand).

• Abnormal usage of legitimate binaries (e.g., regsvr32.exe without DLL registration, or mshta.exe executing remote scripts).

• Unusual scheduled tasks or registry entries referencing scripts or indirect command execution methods.

Why it is Important to Detect This Technique

Early detection of Indirect Command Execution is critical due to its potentially severe impacts on systems and networks:

• Evasion of Traditional Security Controls

  • Indirect command execution often bypasses antivirus and signature-based detection, allowing attackers prolonged access without detection.

• Persistence and Long-Term Compromise

  • Attackers frequently use indirect execution techniques to establish persistent footholds, making remediation more difficult and costly.

• Privilege Escalation and Lateral Movement

  • Enables attackers to escalate privileges or move laterally within networks, significantly increasing the scope and severity of compromise.

• Data Exfiltration and Damage

  • Facilitates stealthy data exfiltration, espionage, and sabotage operations, potentially causing significant financial and reputational damage.

• Compliance and Regulatory Risks

  • Undetected indirect command execution can lead to regulatory non-compliance (e.g., GDPR, HIPAA), resulting in fines, penalties, and reputational harm.

Examples

Real-world examples demonstrating Indirect Command Execution include:

• APT29 (Cozy Bear)

  • Leveraged PowerShell and WMI for indirect command execution and lateral movement within compromised networks.

  • Utilized encoded PowerShell commands and reflective loading techniques to execute payloads indirectly and evade detection.

• FIN7 Group

  • Utilized malicious Microsoft Office macros embedded within documents to indirectly execute payloads through legitimate scripting engines.

  • Employed JavaScript and VBScript via wscript.exe and cscript.exe for stealthy command execution and persistence.

• Emotet Malware

  • Used indirect execution through malicious macros in Microsoft Office documents, invoking PowerShell scripts to download and execute additional payloads.

  • Frequently leveraged obfuscation and indirect execution methods to evade traditional antivirus solutions.

• TrickBot Malware

  • Employed indirect command execution via scheduled tasks, registry modifications, and legitimate Windows utilities (e.g., regsvr32.exe) to execute malicious payloads.

  • Utilized PowerShell and scripting interpreters to indirectly load malware into memory, avoiding detection by endpoint security tools.

• Cobalt Strike Framework

  • Attackers frequently use Cobalt Strike to indirectly execute commands via reflective DLL injection, PowerShell scripts, and legitimate Windows binaries.

  • Indirect command execution through trusted binaries and scripting languages enables attackers to evade detection and maintain persistent access.