Emond

Emond [T1546.014]

Information

• Name: Emond

• ID: T1546.014

• Tactics: TA0004, TA0003

• Technique: T1546

Introduction

Emond (Event Monitor Daemon) [T1546.014] is a sub-technique within the MITRE ATT&CK framework categorized under Persistence. Attackers leverage Emond, a built-in macOS service that monitors specified system events and executes actions based on defined rules, to maintain persistence on compromised macOS systems. By modifying or creating Emond rules, adversaries can execute malicious scripts or binaries automatically without user interaction, thus enabling long-term footholds within victim environments.

Deep Dive Into Technique

Emond (Event Monitor Daemon) is a native macOS service designed to monitor system events and trigger predefined actions. The daemon reads configuration files located in the directory:

• /etc/emond.d/rules/

These files define event monitoring rules in plist (property list) XML format. Each rule specifies the conditions (events) to monitor and the actions to execute when those conditions are met.

Attackers exploit this functionality by:

1. Creating or modifying existing Emond rule files to trigger malicious scripts or binaries upon certain system events or periodically.

2. Ensuring the malicious payload is placed in a hidden or obscure location to evade detection.

3. Leveraging system-level privileges (often gained through privilege escalation) to modify these files, as administrative privileges are required to alter Emond configurations.

Typical execution flow:

• Attacker gains elevated privileges on the macOS system.

• Attacker creates or modifies Emond rule files in /etc/emond.d/rules/.

• Malicious Emond rule triggers execution of attacker-controlled scripts or binaries upon system events, such as startup, user login, or specific scheduled intervals.

• The malicious payload executes silently, maintaining persistent access and control over the compromised host.

When this Technique is Usually Used

Attackers typically employ Emond [T1546.014] during the following stages and scenarios:

• Persistence Stage: Establishing long-term, stealthy persistence after initial compromise.

• Privilege Escalation Scenario: After gaining administrative privileges, attackers leverage Emond to maintain elevated persistence.

• Post-Exploitation Scenario: Maintaining persistent access to macOS systems for lateral movement, reconnaissance, or data exfiltration.

• Stealthy Operations: Due to Emond's legitimate use in macOS, attackers exploit it to blend malicious activities with normal system behavior, thereby reducing the likelihood of detection.

How this Technique is Usually Detected

Detection of malicious Emond usage involves multiple methodologies and tools:

• File Integrity Monitoring (FIM): Monitor changes to Emond rule directories (/etc/emond.d/rules/) for unauthorized modifications or newly created files.

• Audit Logging and Monitoring: Enable audit logging with macOS built-in auditd or third-party endpoint detection solutions to detect suspicious file creations or modifications in Emond rule directories.

• Endpoint Detection and Response (EDR) Tools: Utilize EDR solutions capable of detecting anomalous processes and file modifications related to Emond.

• Behavioral Analysis: Look for unexpected or unusual processes spawned by Emond, especially scripts or binaries executing from uncommon locations.

• System Event Logs: Regularly review system logs for anomalies or unexpected executions triggered by Emond.

Specific Indicators of Compromise (IoCs):

• Unauthorized or unusual plist files appearing in /etc/emond.d/rules/.

• Suspicious scripts or binaries located in hidden directories or unusual paths triggered by Emond rules.

• Increased or abnormal Emond daemon activity in system logs or monitoring tools.

• Unusual network connections or outbound traffic initiated by processes spawned by Emond rules.

Why it is Important to Detect This Technique

Timely detection of Emond-based persistence is critical due to the following potential impacts:

• Long-term Persistence: Attackers leveraging Emond can maintain persistent access over extended periods, enabling ongoing data exfiltration, lateral movement, or espionage activities.

• Stealth and Evasion: Emond misuse is challenging to detect as it leverages legitimate macOS functionality, significantly increasing the risk of prolonged compromise.

• Privilege Abuse: Attackers typically require elevated privileges to manipulate Emond rules, indicating a deeper compromise level and potential for further privilege escalation or damage.

• Data Exfiltration Risk: Persistent access via Emond can lead to theft of sensitive information, intellectual property, or personal data, causing severe financial and reputational damage.

• System Integrity Compromise: Unauthorized Emond rules can alter system behavior, degrade system performance, and compromise the integrity of macOS systems, potentially leading to operational disruptions.

Early detection and mitigation of this technique help prevent attackers from maintaining long-term footholds, minimize damage, and reduce the likelihood of extensive compromise.

Examples

Real-world examples and scenarios involving Emond [T1546.014]:

• XCSSET Malware:

  • Attack Scenario: XCSSET malware targeted macOS developers by injecting malicious payloads into Xcode projects.

  • Technique Usage: Leveraged Emond daemon rules to persistently execute malicious scripts upon system events, ensuring continuous access and reinfection capabilities.

  • Tools/Methods Used: Malicious plist files placed in /etc/emond.d/rules/, executing hidden scripts to maintain persistence.

  • Impact: Persistent backdoor access, theft of sensitive developer data, and potential further compromise of development environments.

• OSX.Dok Malware:

  • Attack Scenario: OSX.Dok malware distributed via phishing emails with malicious attachments targeting macOS users.

  • Technique Usage: Manipulated Emond rules to achieve persistent execution of the malware after initial infection.

  • Tools/Methods Used: Malicious Emond plist files triggering execution of scripts that established command-and-control (C2) communication.

  • Impact: Persistent unauthorized access, credential theft, interception of web traffic, and potential financial loss or data exfiltration.

• WindTail Malware (OceanLotus/APT32):

  • Attack Scenario: Advanced persistent threat group OceanLotus used WindTail malware to target macOS users, including activists and organizations.

  • Technique Usage: Used Emond rule files to ensure persistent execution of malicious payloads upon system events.

  • Tools/Methods Used: Emond plist files triggering hidden binaries and scripts for persistent backdoor access.

  • Impact: Persistent espionage activities, sensitive data exfiltration, surveillance, and potential operational disruption.

These examples highlight the real-world exploitation of Emond by sophisticated adversaries, underscoring the importance of monitoring and detecting this persistence technique.