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  1. Frameworks
  2. >ATTACK
  3. >Credential Access
  4. >ATTACK-T1556.005
ATTACK-T1556.005Active

Reversible Encryption

Statement

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:

  1. Encrypted password (<code>G$RADIUSCHAP</code>) from the Active Directory user-structure <code>userParameters</code>
  2. 16 byte randomly-generated value (<code>G$RADIUSCHAPKEY</code>) also from <code>userParameters</code>
  3. Global LSA secret (<code>G$MSRADIUSCHAPKEY</code>)
  4. Static key hardcoded in the Remote Access Subauthentication DLL (<code>RASSFM.DLL</code>)

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>.

Location

Tactic
Credential Access

Technique Details

Identifier
ATTACK-T1556.005
Parent Technique
ATTACK-T1556
ATT&CK Page
View on MITRE

Tactics

Credential AccessDefense EvasionPersistence

Platforms

Windows

Detection

Detect Modification of Authentication Process via Reversible Encryption

Mitigations

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.

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:

  • 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.
SP 800-53
SP800-53-AC-2relatedvia ctid-attack-to-sp800-53
SP800-53-AC-5relatedvia ctid-attack-to-sp800-53
SP800-53-AC-6relatedvia ctid-attack-to-sp800-53
SP800-53-IA-5relatedvia ctid-attack-to-sp800-53
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Credential Access62 controls
ATTACK-T1003OS Credential DumpingATTACK-T1003.001LSASS MemoryATTACK-T1003.002Security Account ManagerATTACK-T1003.003NTDSATTACK-T1003.004LSA SecretsATTACK-T1003.005Cached Domain CredentialsATTACK-T1003.006DCSyncATTACK-T1003.007Proc FilesystemATTACK-T1003.008/etc/passwd and /etc/shadowATTACK-T1040Network SniffingATTACK-T1110Brute ForceATTACK-T1110.001Password GuessingATTACK-T1110.002Password CrackingATTACK-T1110.003Password SprayingATTACK-T1110.004Credential StuffingATTACK-T1111Multi-Factor Authentication InterceptionATTACK-T1187Forced AuthenticationATTACK-T1212Exploitation for Credential AccessATTACK-T1528Steal Application Access TokenATTACK-T1539Steal Web Session CookieATTACK-T1552Unsecured CredentialsATTACK-T1552.001Credentials In FilesATTACK-T1552.002Credentials in RegistryATTACK-T1552.003Shell HistoryATTACK-T1552.004Private KeysATTACK-T1552.005Cloud Instance Metadata APIATTACK-T1552.006Group Policy PreferencesATTACK-T1552.007Container APIATTACK-T1552.008Chat MessagesATTACK-T1555Credentials from Password StoresATTACK-T1555.001KeychainATTACK-T1555.002Securityd MemoryATTACK-T1555.003Credentials from Web BrowsersATTACK-T1555.004Windows Credential ManagerATTACK-T1555.005Password ManagersATTACK-T1555.006Cloud Secrets Management StoresATTACK-T1556Modify Authentication ProcessATTACK-T1556.001Domain Controller AuthenticationATTACK-T1556.002Password Filter DLLATTACK-T1556.003Pluggable Authentication ModulesATTACK-T1556.004Network Device AuthenticationATTACK-T1556.005Reversible EncryptionATTACK-T1556.006Multi-Factor AuthenticationATTACK-T1556.007Hybrid IdentityATTACK-T1556.008Network Provider DLLATTACK-T1556.009Conditional Access PoliciesATTACK-T1557Adversary-in-the-MiddleATTACK-T1557.001LLMNR/NBT-NS Poisoning and SMB RelayATTACK-T1557.002ARP Cache PoisoningATTACK-T1557.003DHCP SpoofingATTACK-T1557.004Evil TwinATTACK-T1558Steal or Forge Kerberos TicketsATTACK-T1558.001Golden TicketATTACK-T1558.002Silver TicketATTACK-T1558.003KerberoastingATTACK-T1558.004AS-REP RoastingATTACK-T1558.005Ccache FilesATTACK-T1606Forge Web CredentialsATTACK-T1606.001Web CookiesATTACK-T1606.002SAML TokensATTACK-T1621Multi-Factor Authentication Request GenerationATTACK-T1649Steal or Forge Authentication Certificates