LC_LOAD_DYLIB Addition
LC_LOAD_DYLIB Addition [T1546.006]
Information
Name: LC_LOAD_DYLIB Addition
ID: T1546.006
Technique: T1546
Introduction
LC_LOAD_DYLIB Addition (T1546.006) is a sub-technique within the MITRE ATT&CK framework under the broader Persistence technique category (T1546). It refers to adversaries modifying Mach-O binaries on macOS systems by adding malicious dynamic libraries (dylibs) to the LC_LOAD_DYLIB load commands. This modification allows attackers to execute malicious payloads persistently whenever the infected binary is executed, thus maintaining persistence and potentially escalating privileges.
Deep Dive Into Technique
Mach-O (Mach Object) binaries are executable files used by macOS and iOS operating systems. These binaries can dynamically load libraries (dylibs) at runtime using load commands such as LC_LOAD_DYLIB. Attackers exploit this functionality by inserting additional LC_LOAD_DYLIB commands into legitimate binaries, causing the system to load malicious dylibs during the binary's execution.
Technical details of this sub-technique include:
Mach-O Binary Structure:
Mach-O binaries contain headers and load commands that define how the binary loads and executes.
Load commands specify dependencies, entry points, and memory layout information.
LC_LOAD_DYLIB commands specifically instruct the operating system to load dynamic libraries at runtime.
Modification Methods:
Attackers typically use tools such as
install_name_toolor custom scripts to insert malicious dylib references into existing Mach-O binaries.Malicious dylibs are usually placed in inconspicuous locations on the filesystem to evade detection.
Attackers may alter system binaries, third-party applications, or custom binaries to ensure persistent execution.
Execution Mechanism:
When the modified binary executes, macOS automatically loads the malicious dylib into memory.
The malicious dylib code runs in the context of the host binary, inheriting its permissions and privileges.
This method allows attackers to gain persistence, escalate privileges, or execute arbitrary code without additional user interaction.
When this Technique is Usually Used
Attackers commonly leverage LC_LOAD_DYLIB addition in various attack scenarios and stages, including:
Persistence:
Establishing persistence by modifying frequently executed binaries or system utilities.
Ensuring malicious code execution persists across system reboots and user logins.
Privilege Escalation:
Modifying binaries with higher privileges (e.g., binaries executed by root or system-level processes) to escalate privileges.
Defense Evasion:
Embedding malicious code within legitimate binaries to evade traditional security controls and antivirus detection.
Avoiding suspicion by leveraging trusted binaries already present on the system.
Initial Access and Execution:
Post-compromise scenario: adversaries who have already gained initial access may use this technique to maintain long-term control over the compromised system.
How this Technique is Usually Detected
Detection of LC_LOAD_DYLIB addition typically involves monitoring and analyzing system binaries, load commands, and filesystem changes. Detection methods and indicators of compromise (IoCs) include:
File Integrity Monitoring (FIM):
Using tools like Tripwire, OSSEC, or built-in macOS tools to detect unauthorized modifications to system binaries.
Monitoring changes to binary load commands or the addition of new dylib references.
Binary Analysis:
Analyzing Mach-O binaries with tools such as
otool,MachOView, ornmto detect unexpected LC_LOAD_DYLIB entries.Comparing known good binaries with potentially compromised binaries to identify anomalies.
Endpoint Detection and Response (EDR):
Utilizing EDR solutions capable of detecting suspicious binary modifications or anomalous binary execution patterns.
Monitoring process execution logs and binary load events for suspicious activities.
Behavioral Monitoring:
Observing unexpected behavior of known binaries, such as unusual network connections, privilege escalations, or access to sensitive files.
Detecting anomalies in process behavior through system monitoring tools (e.g., Activity Monitor, audit logs).
Indicators of Compromise (IoCs):
Unexpected dylibs in unusual filesystem locations, such as hidden directories or user home directories.
Modified timestamps or file hashes of system binaries, indicating unauthorized changes.
Suspicious LC_LOAD_DYLIB entries referencing unknown or suspicious dylib paths.
Why it is Important to Detect This Technique
Detecting LC_LOAD_DYLIB addition is critical due to its significant impact on system security and stability. The importance of early detection includes:
Preventing Persistent Access:
Early detection prevents attackers from maintaining persistent access to compromised systems, limiting their ability to carry out further malicious actions.
Reducing Privilege Escalation Risks:
Detection mitigates the risk of attackers escalating privileges by compromising high-privileged binaries or system utilities.
Avoiding Data Exfiltration and Espionage:
Malicious dylibs may include functionalities such as keylogging, credential theft, or data exfiltration. Early detection prevents the loss of sensitive information.
Minimizing System Instability and Damage:
Unauthorized modifications to system binaries can cause instability, crashes, or performance degradation. Detecting this technique helps maintain system integrity and reliability.
Compliance and Security Posture:
Detecting and responding to this technique helps organizations maintain compliance with regulatory requirements and uphold strong security practices.
Examples
Real-world examples and known attack scenarios involving LC_LOAD_DYLIB addition include:
XcodeGhost Malware (2015):
Attackers modified Apple's Xcode development environment by adding malicious dylib references to legitimate binaries within Xcode.
Developers unknowingly compiled and distributed compromised iOS apps containing malicious dylibs, leading to widespread infections.
Impact: Data exfiltration, remote command execution, and credential theft from millions of users.
OSX/Shlayer Malware (2019-2020):
Shlayer malware utilized malicious dylibs inserted into legitimate binaries via LC_LOAD_DYLIB modifications to establish persistence on macOS systems.
Attackers distributed malware through deceptive software updates and fake installers.
Impact: Persistent adware infections, browser hijacking, and unauthorized data collection.
OceanLotus (APT32) macOS Malware:
Advanced Persistent Threat (APT32) group leveraged LC_LOAD_DYLIB additions to compromise macOS systems, embedding malicious dylibs into legitimate binaries.
Targeted espionage campaigns against government, media, and corporate entities.
Impact: Persistent espionage, data exfiltration, and reconnaissance activities.
Tools commonly used by adversaries to perform LC_LOAD_DYLIB addition include:
install_name_tool: Native macOS binary manipulation utility.Custom scripting tools and malware frameworks designed specifically for Mach-O binary manipulation.
These examples demonstrate the severity and practical implications of LC_LOAD_DYLIB addition, highlighting the importance of proactive detection and mitigation.
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