Active Directory Authentication Protocols: Understanding Security Risks and Solutions

What is AD Authentication and How Does it Work?

Active Directory authentication allows IT teams to authenticate and authorize users, endpoints, and services to Active Directory. It streamlines user and rights management and provides centralized control over devices and user configurations. It also offers single sign-on functionality and replaces weak protocols with more secure ones.

Active Directory authentication typically incorporates two standards, namely Kerberos and Lightweight Directory Access Protocol (LDAP), which are explained in more detail below.

1. Kerberos protocol

Kerberos-based authentication allows users to log in only once to access enterprise resources, using a session key that lasts for a designated period. The system also generates a token that contains access policies and rights to ensure users only access authorized resources. To connect to the AD server or domain controller, clients must authenticate themselves to a trusted third party called the key distribution center (KDC). The KDC includes an authentication server (AS) and a ticket granting server (TGS). The AS authenticates clients to the network by encrypting their login credentials with their password’s secret key. The AS sends the client a ticket granting ticket (TGT) after successful authentication. The TGS decrypts the TGT and issues a token to the client encrypted with a different key. The client then transmits the token to the target server, which decrypts it to allow access to resources for a limited time.

2. Lightweight Directory Access Protocol

LDAP is a protocol that supports AD authentication services and is both open source and cross-platform. LDAP-based authentication in AD offers two choices: simple authentication and simple authentication with security layer (SASL). With simple authentication, LDAP generates a server request based on login credentials, and it also allows anonymous and unauthenticated requests to resources. SASL, on the other hand, utilizes other authentication services like Kerberos to connect to the LDAP server. IT teams can employ this method for enhanced security as it decouples authentication methods from application protocols.

Authenticating Linux Devices Through Active Directory

Active Directory seamlessly integrates with Windows-based systems and services, but as Linux and macOS become more popular, centralized access management of these platforms has become necessary. To connect Linux devices to AD, you will need to reconfigure them to leverage the LDAP’s pluggable authentication module (PAM). Another option is Samba – a Windows interoperability tool that supports Active Directory authentication in Linux machines. Samba can also create domains, set up a shared print server, and configure PAM for local authentication.

Authenticating Macs Through AD

IT teams can use an LDAP/AD connector to connect Macs to Active Directory infrastructure. The AD connector also maps AD identities to macOS IAM roles for federated SSO. However, macOS 10.12 or later cannot join an AD domain without Windows Server 2008+ domain services.

Shortcomings of Active Directory Authentication

In the past, device management and authentication were mainly focused on Windows OSs and AD, but with the emergence of Linux, macOS, and cloud-based infrastructure, managing access controls in a heterogeneous environment has become more challenging. Legacy AD authentication has resulted in multiple, smaller directories being used instead of one centralized platform. The adoption of SaaS applications also adds challenges to IAM with siloed applications and complicated onboarding processes. It should also be noted that, in order to connect a Mac to AD, IT teams must enable weak cryptography, which is not good for security.

Security Risks Associated with AD Authentication Protocols

While Active Directory authentication protocols are relatively secure, they are not immune to security risks. The following are some of the common security risks associated with these protocols:

1. Password-based attacks: Password-based attacks are a common method used by attackers to gain unauthorized access to AD resources. They include dictionary attacks, brute force attacks, and password spraying. Password spraying, in particular, is a type of attack where the attacker tries a few commonly used passwords against many user accounts, hoping someone used a weak password.

2. Man-in-the-middle attacks: Man-in-the-middle attacks involve an attacker intercepting communication between two parties and impersonating one or both parties, often in an attempt to steal login credentials.

3. Pass-the-hash attacks: Pass-the-hash attacks involve an attacker extracting password hashes from a compromised system and using them to authenticate to other systems without the need for the actual password.

4. Weak authentication settings: Weak authentication settings, such as allowing weak passwords or not enforcing multi-factor authentication, can make it easier for attackers to gain unauthorized access to sensitive resources.

Solutions to Mitigate Security Risks

To mitigate the security risks associated with Active Directory authentication protocols, it is important to implement the right security controls. Below are the most notable solutions:

1. Strong Password Policies: Enforcing strong password policies that require users to use complex passwords and change them regularly can make it harder for attackers to guess or crack passwords.

2. Multi-factor Authentication (MFA): MFA is an authentication process that requires at least two forms of authentication to verify identity. This can include something the user knows (e.g., a password) and something the user has (e.g., a token or smart card). Implementing MFA can significantly improve the security of AD authentication protocols.

3. Encryption: Encrypting all communication between client and server using Secure Socket Layer (SSL) or Transport Layer Security (TLS) can protect against man-in-the-middle attacks.

4. Least Privilege Access: Applying the principle of least privilege (PoLP) can minimize the risk of pass-the-hash attacks. This can be done by limiting user access to only the resources they need to do their job.

5. Privileged Account Monitoring: Use a real-time auditing solution to help you identify anomalous privileged account activity. This includes identifying over-privileged users, inactive users/computers, open shares, legacy issues, passwords that never expire, and more.

How Lepide Helps Secure Active Directory

Lepide Auditor for Active Directory is a real-time AD auditing tool that assists you in identifying your privileged users and keeping track of how they interact with sensitive data. It also allows you to audit logon/logoff activity and manage password resets. Our platform helps you locate your most critical assets, allowing you to make informed decisions on which users should have access to which resources. Our solution can detect and alert on trends in user behavior, and identify any excessive permissions. It also generates Account Lockout Reports, which can help you determine the cause of the lockouts and reset the password or unlock the accounts remotely. With its remote management capability, it is easy to manage user and service accounts in Active Directory, particularly in time-sensitive scenarios.