An adversary may abuse Active Directory authentication encryption properties to gain access to credentials on Windows systems. The <code>AllowReversiblePasswordEncryption</code> property specifies whether reversible password encryption for an account is enabled or disabled. By default this property is disabled (instead storing user credentials as the output of one-way hashing functions) and should not be enabled unless legacy or other software require it.(Citation: store_pwd_rev_enc)
If the property is enabled and/or a user changes their password after it is enabled, an adversary may be able to obtain the plaintext of passwords created/changed after the property was enabled. To decrypt the passwords, an adversary needs four components:
With this information, an adversary may be able to reproduce the encryption key and subsequently decrypt the encrypted password value.(Citation: how_pwd_rev_enc_1)(Citation: how_pwd_rev_enc_2)
An adversary may set this property at various scopes through Local Group Policy Editor, user properties, Fine-Grained Password Policy (FGPP), or via the ActiveDirectory PowerShell module. For example, an adversary may implement and apply a FGPP to users or groups if the Domain Functional Level is set to "Windows Server 2008" or higher.(Citation: dump_pwd_dcsync) In PowerShell, an adversary may make associated changes to user settings using commands similar to <code>Set-ADUser -AllowReversiblePasswordEncryption $true</code>.
Detect Modification of Authentication Process via Reversible Encryption
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:
Credential Security:
Multi-Factor Authentication (MFA):
Privileged Access Management (PAM):
Auditing and Monitoring:
Just-In-Time Access:
Tools for Implementation
Privileged Access Management (PAM):
Credential Management:
Multi-Factor Authentication:
Linux Privilege Management:
Just-In-Time Access:
Password Policies: 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:
Linux Systems:
pam_pwquality to enforce complexity and length requirements.pam_tally2 or pam_faillock for account lockouts.pwunconv to disable password reuse.Password Managers:
Password Blacklisting:
Regular Auditing:
Tools for Implementation
Windows:
Linux/macOS:
Cross-Platform: