Adversaries may use bootkits to persist on systems. A bootkit is a malware variant that modifies the boot sectors of a hard drive, allowing malicious code to execute before a computer's operating system has loaded. Bootkits reside at a layer below the operating system and may make it difficult to perform full remediation unless an organization suspects one was used and can act accordingly. In BIOS systems, a bootkit may modify the Master Boot Record (MBR) and/or Volume Boot Record (VBR).(Citation: Mandiant M Trends 2016) The MBR is the section of disk that is first loaded after completing hardware initialization by the BIOS. It is the location of the boot loader. An adversary who has raw access to the boot drive may overwrite this area, diverting execution during startup from the normal boot loader to adversary code.(Citation: Lau 2011) The MBR passes control of the boot process to the VBR. Similar to the case of MBR, an adversary who has raw access to the boot drive may overwrite the VBR to divert execution during startup to adversary code. In UEFI (Unified Extensible Firmware Interface) systems, a bootkit may instead create or modify files in the EFI system partition (ESP). The ESP is a partition on data storage used by devices containing UEFI that allows the system to boot the OS and other utilities used by the system. An adversary can use the newly created or patched files in the ESP to run malicious kernel code.(Citation: Microsoft Security)(Citation: welivesecurity)
Detection of suspicious write operations to block devices, modifications of bootloader files (GRUB, initrd, vmlinuz), and unexpected changes within the EFI System Partition. Monitors privileged execution of utilities like dd, grub-install, or efibootmgr that modify boot sectors or loader entries.
Detection of raw access to physical drives, modification of boot records (MBR/VBR), and suspicious file creation or alteration within the EFI System Partition (ESP). Correlates privileged process execution with low-level disk modification and unexpected driver or firmware interactions.
Privileged Account Management
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.
Boot Integrity
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.