T1601.002: Downgrade System Image

Multi-Factor Authentication (MFA) enhances security by requiring users to provide at least two forms of verification to prove their identity before granting access. These factors typically include:

- *Something you know*: Passwords, PINs. - *Something you have*: Physical tokens, smartphone authenticator apps. - *Something you are*: Biometric data such as fingerprints, facial recognition, or retinal scans.

Implementing MFA across all critical systems and services ensures robust protection against account takeover and unauthorized access. This mitigation can be implemented through the following measures:

Identity and Access Management (IAM):

- Use IAM solutions like Azure Active Directory, Okta, or AWS IAM to enforce MFA policies for all user logins, especially for privileged roles. - Enable conditional access policies to enforce MFA for risky sign-ins (e.g., unfamiliar devices, geolocations). - Enable Conditional Access policies to only allow logins from trusted devices, such as those enrolled in Intune or joined via Hybrid/Entra.

Authentication Tools and Methods:

- Use authenticator applications such as Google Authenticator, Microsoft Authenticator, or Authy for time-based one-time passwords (TOTP). - Deploy hardware-based tokens like YubiKey, RSA SecurID, or smart cards for additional security. - Enforce biometric authentication for compatible devices and applications.

Secure Legacy Systems:

- Integrate MFA solutions with older systems using third-party tools like Duo Security or Thales SafeNet. - Enable RADIUS/NPS servers to facilitate MFA for VPNs, RDP, and other network logins.

Monitoring and Alerting:

- Use SIEM tools to monitor failed MFA attempts, login anomalies, or brute-force attempts against MFA systems. - Implement alerts for suspicious MFA activities, such as repeated failed codes or new device registrations.

Training and Policy Enforcement:

- Educate employees on the importance of MFA and secure authenticator usage. - Enforce policies that require MFA on all critical systems, especially for remote access, privileged accounts, and cloud applications.

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.

Credential Access Protection focuses on implementing measures to prevent adversaries from obtaining credentials, such as passwords, hashes, tokens, or keys, that could be used for unauthorized access. This involves restricting access to credential storage mechanisms, hardening configurations to block credential dumping methods, and using monitoring tools to detect suspicious credential-related activity. This mitigation can be implemented through the following measures:

Restrict Access to Credential Storage:

- Use Case: Prevent adversaries from accessing the SAM (Security Account Manager) database on Windows systems. - Implementation: Enforce least privilege principles and restrict administrative access to credential stores such as `C:\Windows\System32\config\SAM`.

Use Credential Guard:

- Use Case: Isolate LSASS (Local Security Authority Subsystem Service) memory to prevent credential dumping. - Implementation: Enable Windows Defender Credential Guard on enterprise endpoints to isolate secrets and protect them from unauthorized access.

Monitor for Credential Dumping Tools:

- Use Case: Detect and block known tools like Mimikatz or Windows Credential Editor. - Implementation: Flag suspicious process behavior related to credential dumping.

Disable Cached Credentials:

- Use Case: Prevent adversaries from exploiting cached credentials on endpoints. - Implementation: Configure group policy to reduce or eliminate the use of cached credentials (e.g., set Interactive logon: Number of previous logons to cache to 0).

Enable Secure Boot and Memory Protections:

- Use Case: Prevent memory-based attacks used to extract credentials. - Implementation: Configure Secure Boot and enforce hardware-based security features like DEP (Data Execution Prevention) and ASLR (Address Space Layout Randomization).

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.

Set and enforce secure password policies for accounts to reduce the likelihood of unauthorized access. Strong password policies include enforcing password complexity, requiring regular password changes, and preventing password reuse. This mitigation can be implemented through the following measures:

Windows Systems:

- Use Group Policy Management Console (GPMC) to configure: - Minimum password length (e.g., 12+ characters). - Password complexity requirements. - Password history (e.g., disallow last 24 passwords). - Account lockout duration and thresholds.

Linux Systems:

- Configure Pluggable Authentication Modules (PAM): - Use `pam_pwquality` to enforce complexity and length requirements. - Implement `pam_tally2` or `pam_faillock` for account lockouts. - Use `pwunconv` to disable password reuse.

Password Managers:

- Enforce usage of enterprise password managers (e.g., Bitwarden, 1Password, LastPass) to generate and store strong passwords.

Password Blacklisting:

- Use tools like Have I Been Pwned password checks or NIST-based blacklist solutions to prevent users from setting compromised passwords.

Regular Auditing:

- Periodically audit password policies and account configurations to ensure compliance using tools like LAPS (Local Admin Password Solution) and vulnerability scanners.

*Tools for Implementation*

Windows:

- Group Policy Management Console (GPMC): Enforce password policies. - Microsoft Local Administrator Password Solution (LAPS): Enforce random, unique admin passwords.

Linux/macOS:

- PAM Modules (pam_pwquality, pam_tally2, pam_faillock): Enforce password rules. - Lynis: Audit password policies and system configurations.

Cross-Platform:

- Password Managers (Bitwarden, 1Password, KeePass): Manage and enforce strong passwords. - Have I Been Pwned API: Prevent the use of breached passwords. - NIST SP 800-63B compliant tools: Enforce password guidelines and blacklisting.

Boot Integrity ensures that a system starts securely by verifying the integrity of its boot process, operating system, and associated components. This mitigation focuses on leveraging secure boot mechanisms, hardware-rooted trust, and runtime integrity checks to prevent tampering during the boot sequence. It is designed to thwart adversaries attempting to modify system firmware, bootloaders, or critical OS components. This mitigation can be implemented through the following measures:

Implementation of Secure Boot:

- Implementation: Enable UEFI Secure Boot on all systems and configure it to allow only signed bootloaders and operating systems. - Use Case: An adversary attempts to replace the system’s bootloader with a malicious version to gain persistence. Secure Boot prevents the untrusted bootloader from executing, halting the attack.

Utilization of TPMs:

- Implementation: Configure systems to use TPM-based attestation for boot integrity, ensuring that any modification to the firmware, bootloader, or OS is detected. - Use Case: A compromised firmware component alters the boot sequence. The TPM detects the change and triggers an alert, allowing the organization to respond before further damage.

Enable Bootloader Passwords:

- Implementation: Protect BIOS/UEFI settings with a strong password and limit physical access to devices. - Use Case: An attacker with physical access attempts to disable Secure Boot or modify the boot sequence. The password prevents unauthorized changes.

Runtime Integrity Monitoring:

- Implementation: Deploy solutions to verify the integrity of critical files and processes after boot. - Use Case: A malware infection modifies kernel modules post-boot. Runtime integrity monitoring detects the modification and prevents the malicious module from loading.