T1553: Subvert Trust Controls

Operating System Configuration involves adjusting system settings and hardening the default configurations of an operating system (OS) to mitigate adversary exploitation and prevent abuse of system functionality. Proper OS configurations address security vulnerabilities, limit attack surfaces, and ensure robust defense against a wide range of techniques. This mitigation can be implemented through the following measures:

Disable Unused Features:

- Turn off SMBv1, LLMNR, and NetBIOS where not needed. - Disable remote registry and unnecessary services.

Enforce OS-level Protections:

- Enable Data Execution Prevention (DEP), Address Space Layout Randomization (ASLR), and Control Flow Guard (CFG) on Windows. - Use AppArmor or SELinux on Linux for mandatory access controls.

Secure Access Settings:

- Enable User Account Control (UAC) for Windows. - Restrict root/sudo access on Linux/macOS and enforce strong permissions using sudoers files.

File System Hardening:

- Implement least-privilege access for critical files and system directories. - Audit permissions regularly using tools like icacls (Windows) or getfacl/chmod (Linux/macOS).

Secure Remote Access:

- Restrict RDP, SSH, and VNC to authorized IPs using firewall rules. - Enable NLA for RDP and enforce strong password/lockout policies.

Harden Boot Configurations:

- Enable Secure Boot and enforce UEFI/BIOS password protection. - Use BitLocker or LUKS to encrypt boot drives.

Regular Audits:

- Periodically audit OS configurations using tools like CIS Benchmarks or SCAP tools.

*Tools for Implementation*

Windows:

- Microsoft Group Policy Objects (GPO): Centrally enforce OS security settings. - Windows Defender Exploit Guard: Built-in OS protection against exploits. - CIS-CAT Pro: Audit Windows security configurations based on CIS Benchmarks.

Linux/macOS:

- AppArmor/SELinux: Enforce mandatory access controls. - Lynis: Perform comprehensive security audits. - SCAP Security Guide: Automate configuration hardening using Security Content Automation Protocol.

Cross-Platform:

- Ansible or Chef/Puppet: Automate configuration hardening at scale. - OpenSCAP: Perform compliance and configuration checks.

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.

Privileged Account Management focuses on implementing policies, controls, and tools to securely manage privileged accounts (e.g., SYSTEM, root, or administrative accounts). This includes restricting access, limiting the scope of permissions, monitoring privileged account usage, and ensuring accountability through logging and auditing.This mitigation can be implemented through the following measures:

Account Permissions and Roles:

- Implement RBAC and least privilege principles to allocate permissions securely. - Use tools like Active Directory Group Policies to enforce access restrictions.

Credential Security:

- Deploy password vaulting tools like CyberArk, HashiCorp Vault, or KeePass for secure storage and rotation of credentials. - Enforce password policies for complexity, uniqueness, and expiration using tools like Microsoft Group Policy Objects (GPO).

Multi-Factor Authentication (MFA):

- Enforce MFA for all privileged accounts using Duo Security, Okta, or Microsoft Azure AD MFA.

Privileged Access Management (PAM):

- Use PAM solutions like CyberArk, BeyondTrust, or Thycotic to manage, monitor, and audit privileged access.

Auditing and Monitoring:

- Integrate activity monitoring into your SIEM (e.g., Splunk or QRadar) to detect and alert on anomalous privileged account usage.

Just-In-Time Access:

- Deploy JIT solutions like Azure Privileged Identity Management (PIM) or configure ephemeral roles in AWS and GCP to grant time-limited elevated permissions.

*Tools for Implementation*

Privileged Access Management (PAM):

- CyberArk, BeyondTrust, Thycotic, HashiCorp Vault.

Credential Management:

- Microsoft LAPS (Local Admin Password Solution), Password Safe, HashiCorp Vault, KeePass.

Multi-Factor Authentication:

- Duo Security, Okta, Microsoft Azure MFA, Google Authenticator.

Linux Privilege Management:

- sudo configuration, SELinux, AppArmor.

Just-In-Time Access:

- Azure Privileged Identity Management (PIM), AWS IAM Roles with session constraints, GCP Identity-Aware Proxy.

Restricting registry permissions involves configuring access control settings for sensitive registry keys and hives to ensure that only authorized users or processes can make modifications. By limiting access, organizations can prevent unauthorized changes that adversaries might use for persistence, privilege escalation, or defense evasion. This mitigation can be implemented through the following measures:

Review and Adjust Permissions on Critical Keys

- Regularly review permissions on keys such as `Run`, `RunOnce`, and `Services` to ensure only authorized users have write access. - Use tools like `icacls` or `PowerShell` to automate permission adjustments.

Enable Registry Auditing

- Enable auditing on sensitive keys to log access attempts. - Use Event Viewer or SIEM solutions to analyze logs and detect suspicious activity. - Example Audit Policy: `auditpol /set /subcategory:"Registry" /success:enable /failure:enable`

Protect Credential-Related Hives

- Limit access to hives like `SAM`,`SECURITY`, and `SYSTEM` to prevent credential dumping or other unauthorized access. - Use LSA Protection to add an additional security layer for credential storage.

Restrict Registry Editor Usage

- Use Group Policy to restrict access to regedit.exe for non-administrative users. - Block execution of registry editing tools on endpoints where they are unnecessary.

Deploy Baseline Configuration Tools

- Use tools like Microsoft Security Compliance Toolkit or CIS Benchmarks to apply and maintain secure registry configurations.

*Tools for Implementation*

Registry Permission Tools:

- Registry Editor (regedit): Built-in tool to manage registry permissions. - PowerShell: Automate permissions and manage keys. `Set-ItemProperty -Path "HKLM:\Software\Microsoft\Windows\CurrentVersion\Run" -Name "KeyName" -Value "Value"` - icacls: Command-line tool to modify ACLs.

Monitoring Tools:

- Sysmon: Monitor and log registry events. - Event Viewer: View registry access logs.

Policy Management Tools:

- Group Policy Management Console (GPMC): Enforce registry permissions via GPOs. - Microsoft Endpoint Manager: Deploy configuration baselines for registry permissions.

Software configuration refers to making security-focused adjustments to the settings of applications, middleware, databases, or other software to mitigate potential threats. These changes help reduce the attack surface, enforce best practices, and protect sensitive data. This mitigation can be implemented through the following measures:

Conduct a Security Review of Application Settings:

- Review the software documentation to identify recommended security configurations. - Compare default settings against organizational policies and compliance requirements.

Implement Access Controls and Permissions:

- Restrict access to sensitive features or data within the software. - Enforce least privilege principles for all roles and accounts interacting with the software.

Enable Logging and Monitoring:

- Configure detailed logging for key application events such as authentication failures, configuration changes, or unusual activity. - Integrate logs with a centralized monitoring solution, such as a SIEM.

Update and Patch Software Regularly:

- Ensure the software is kept up-to-date with the latest security patches to address known vulnerabilities. - Use automated patch management tools to streamline the update process.

Disable Unnecessary Features or Services:

- Turn off unused functionality or components that could introduce vulnerabilities, such as debugging interfaces or deprecated APIs.

Test Configuration Changes:

- Perform configuration changes in a staging environment before applying them in production. - Conduct regular audits to ensure that settings remain aligned with security policies.

*Tools for Implementation*

Configuration Management Tools:

- Ansible: Automates configuration changes across multiple applications and environments. - Chef: Ensures consistent application settings through code-based configuration management. - Puppet: Automates software configurations and audits changes for compliance.

Security Benchmarking Tools:

- CIS-CAT: Provides benchmarks and audits for secure software configurations. - Aqua Security Trivy: Scans containerized applications for configuration issues.

Vulnerability Management Solutions:

- Nessus: Identifies misconfigurations and suggests corrective actions.

Logging and Monitoring Tools:

- Splunk: Aggregates and analyzes application logs to detect suspicious activity.