LC_LOAD_DYLIB Addition

Detection Strategy for LC_LOAD_DYLIB Modification in Mach-O Binaries on macOS

Audit: Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations. The primary purpose of auditing is to detect anomalies and identify potential threats or weaknesses in the environment. Proper auditing configurations can also help to meet compliance requirements. The process of auditing encompasses regular analysis of user behaviors and system logs in support of proactive security measures.

Auditing is applicable to all systems used within an organization, from the front door of a building to accessing a file on a fileserver. It is considered more critical for regulated industries such as, healthcare, finance and government where compliance requirements demand stringent tracking of user and system activates.This mitigation can be implemented through the following measures:

System Audit:

• Use Case: Regularly assess system configurations to ensure compliance with organizational security policies.
• Implementation: Use tools to scan for deviations from established benchmarks.

Permission Audits:

• Use Case: Review file and folder permissions to minimize the risk of unauthorized access or privilege escalation.
• Implementation: Run access reviews to identify users or groups with excessive permissions.

Software Audits:

• Use Case: Identify outdated, unsupported, or insecure software that could serve as an attack vector.
• Implementation: Use inventory and vulnerability scanning tools to detect outdated versions and recommend secure alternatives.

Configuration Audits:

• Use Case: Evaluate system and network configurations to ensure secure settings (e.g., disabled SMBv1, enabled MFA).
• Implementation: Implement automated configuration scanning tools like SCAP (Security Content Automation Protocol) to identify non-compliant systems.

Network Audits:

• Use Case: Examine network traffic, firewall rules, and endpoint communications to identify unauthorized or insecure connections.
• Implementation: Utilize tools such as Wireshark, or Zeek to monitor and log suspicious network behavior.

Execution Prevention: Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms. This ensures that only trusted and authorized code is executed, reducing the risk of malware and unauthorized actions. This mitigation can be implemented through the following measures:

Application Control:

• Use Case: Use tools like AppLocker or Windows Defender Application Control (WDAC) to create whitelists of authorized applications and block unauthorized ones. On Linux, use tools like SELinux or AppArmor to define mandatory access control policies for application execution.
• Implementation: Allow only digitally signed or pre-approved applications to execute on servers and endpoints. (e.g., New-AppLockerPolicy -PolicyType Enforced -FilePath "C:\Policies\AppLocker.xml")

Script Blocking:

• Use Case: Use script control mechanisms to block unauthorized execution of scripts, such as PowerShell or JavaScript. Web Browsers: Use browser extensions or settings to block JavaScript execution from untrusted sources.
• Implementation: Configure PowerShell to enforce Constrained Language Mode for non-administrator users. (e.g., Set-ExecutionPolicy AllSigned)

Executable Blocking:

• Use Case: Prevent execution of binaries from suspicious locations, such as %TEMP% or %APPDATA% directories.
• Implementation: Block execution of .exe, .bat, or .ps1 files from user-writable directories.

Dynamic Analysis Prevention:

• Use Case: Use behavior-based execution prevention tools to identify and block malicious activity in real time.
• Implemenation: Employ EDR solutions that analyze runtime behavior and block suspicious code execution.

Code Signing: Code Signing is a security process that ensures the authenticity and integrity of software by digitally signing executables, scripts, and other code artifacts. It prevents untrusted or malicious code from executing by verifying the digital signatures against trusted sources. Code signing protects against tampering, impersonation, and distribution of unauthorized or malicious software, forming a critical defense against supply chain and software exploitation attacks. This mitigation can be implemented through the following measures:

Enforce Signed Code Execution:

• Implementation: Configure operating systems (e.g., Windows with AppLocker or Linux with Secure Boot) to allow only signed code to execute.
• Use Case: Prevent the execution of malicious PowerShell scripts by requiring all scripts to be signed with a trusted certificate.

Vendor-Signed Driver Enforcement:

• Implementation: Enable kernel-mode code signing to ensure that only drivers signed by trusted vendors can be loaded.
• Use Case: A malicious driver attempting to modify system memory fails to load because it lacks a valid signature.

Certificate Revocation Management:

• Implementation: Use Online Certificate Status Protocol (OCSP) or Certificate Revocation Lists (CRLs) to block certificates associated with compromised or deprecated code.
• Use Case: A compromised certificate used to sign a malicious update is revoked, preventing further execution of the software.

Third-Party Software Verification:

• Implementation: Require software from external vendors to be signed with valid certificates before deployment.
• Use Case: An organization only deploys signed and verified third-party software to prevent supply chain attacks.

Script Integrity in CI/CD Pipelines:

• Implementation: Integrate code signing into CI/CD pipelines to sign and verify code artifacts before production release.
• Use Case: A software company ensures that all production builds are signed, preventing tampered builds from reaching customers.

Key Components of Code Signing

• Digital Signature Verification: Verifies the authenticity of code by ensuring it was signed by a trusted entity.
• Certificate Management: Uses Public Key Infrastructure (PKI) to manage signing certificates and revocation lists.
• Enforced Policy for Unsigned Code: Prevents the execution of unsigned or untrusted binaries and scripts.
• Hash Integrity Check: Confirms that code has not been altered since signing by comparing cryptographic hashes.