Man-in-the-middle attacks, also known as MitM attacks, are a form of eavesdropping. These attacks can pose a serious threat to organizations’ network security, particularly in environments that use Microsoft Active Directory (AD) for identity management.

What is a man-in-the-middle attack?

In a man-in-the-middle attack, a malicious actor positions themselves between two parties communicating with each other. These parties can be two users, a user and an application, a workstation and a server computer, and so on.

In these attacks, the attacker essentially controls the traffic. This control enables them to intercept, inspect, and even modify the data being exchanged between two parties, who believe they are communicating directly. This deceit can lead to significant data breaches, exposing sensitive information and providing unauthorized access to network resources.

What is the impact of a man-in-the-middle attack?

The man-in-the-middle attack presents a serious threat. These attacks can be used to steal sensitive information such as login credentials, personal information, or financial data.

Furthermore, an attacker can manipulate the data being transmitted, altering the perceived reality of one or both parties. For example, an attacker might intercept a request to a banking website and change the account details, causing the user to unknowingly deposit money into the attacker’s account.

Man-in-the-middle attacks can take various forms involving Active Directory (AD):

An NTLM relay attack is a type of man-in-the-middle attack that involves the NT LAN Manager (NTLM) authentication process. In this type of attack, the attacker impersonates the victim, gaining unauthorized access to various resources within the network. Mitigation of NTLM relay attacks includes using encrypted protocols, enabling SMB signing, enforcing NTLMv2, and keeping systems up to date with patches.

An LDAP relay attack is a man-in-the-middle attack in which the attacker manipulates Lightweight Directory Access Protocol (LDAP) handling of authentication to impersonate a user and gain unauthorized access to directory information. Protection against LDAP relay attacks involves using secure communication protocols, such as LDAP Secure (LDAPS) or start-TLS, to encrypt data transmission.

A Kerberos unconstrained delegation attack is a man-in-the-middle attack in which an attacker extracts ticket-granting tickets (TGTs) from memory to impersonate authenticated users. To counter this attack, avoid using unconstrained delegation whenever possible and perform regular audits of delegation permissions within AD.

A DNS spoofing attack is a man-in-the-middle attack in which the attacker manipulates the DNS server to divert traffic away from the legitimate server to an attacker-controlled server. Using Domain Name System Security Extensions (NDSSE), which provides DNS response validation, can help to mitigate these attacks.

A pass-the-hash attack is a man-in-the-middle attack that involves an attacker extracting hashed versions of users’ passwords. The attacker uses these passwords to authenticate to other systems on the network. Mitigation steps include enforcing the principle of least privilege; ensuring that system patches are up to date; using strong, unique passwords; and implementing protective measures like the AD Protected Users group and Windows Credential Guard.

How do man-in-the-middle attacks threaten Active Directory?

Beyond these specific attacks, any network-level man-in-the-middle attack can indirectly affect AD. For instance, Address Resolution Protocol (ARP) poisoning can intercept packets on a network, potentially gaining access to data related to AD. Regular monitoring of ARP tables and the use of static ARP can help to prevent such attacks.

Traffic encryption is a crucial defense against man-in-the-middle attacks. Traffic encryption helps to ensure that even intercepted data remains unreadable to unauthorized viewers. Protocols such as LDAP channel binding and LDAP signing and use of LDAPS, start-TLS, and DNSSEC all play a crucial role in maintaining the integrity and confidentiality of data during transmission.

In addition, monitoring processes can help to identify unauthorized or suspicious activities, such as unexpected system processes or unusual account behavior. Regular AD security audits can help you spot potential security risks and ensure that only necessary permissions are granted.

Lastly, continuous monitoring of network traffic is key to spotting anomalies that could indicate a man-in-the-middle attack. Look for abnormal DNS requests and responses or unexpected communication between systems.

Protecting Active Directory from man-in-the-middle attacks

Modern cybersecurity tools play a critical role in monitoring and protecting your AD environment from potential vulnerabilities and threats. Among these, Semperis Directory Services Protector (DSP) and Purple Knight are noteworthy for their sophisticated capabilities designed specifically for AD protection.

Semperis DSP

Semperis DSP is an enterprise-grade cybersecurity solution that provides comprehensive threat mitigation for AD. DSP can monitor and detect unauthorized or suspicious changes in real-time. This monitoring extends to AD objects, configurations, permissions, and even system-level indicators. If an unwanted change occurs, Semperis DSP can notify administrators immediately, providing essential details about the change, including what was modified, who made the change, and when it happened.

Moreover, Semperis DSP has a powerful remediation function that can automatically roll back undesired modifications, restoring the state of your AD environment to its pre-change condition. This rollback capability can greatly reduce the potential damage and disruption caused by unauthorized alterations, whether the result of a misconfiguration or a malicious action.

Purple Knight

Purple Knight enables administrators to perform an extensive vulnerability assessment of their AD infrastructure. By executing periodic scans, Purple Knight evaluates the health of your AD environment against known vulnerabilities and best practices. It provides a detailed report highlighting areas of concern, potential exposures, and suggests remediation steps to harden your AD defenses.

Furthermore, these periodic scans enable continuous tracking of your AD’s security posture. You can use Purple Knight to identify new risks that might arise over time due to changes in your IT environment or the emergence of new threats. As a result, Purple Knight acts as an early warning system, alerting administrators to potential issues before they escalate into significant problems.

Commit to AD security

The potential harm from man-in-the-middle attacks on Active Directory environments underlines the need for organizations to implement robust cybersecurity strategies. Act now by assessing your AD environment and network for vulnerabilities.

Invest in encryption protocols, ensure system patches are current, and strengthen your password policies. Implement monitoring tools that can detect anomalies in system processes and network traffic, and schedule regular security audits to keep your defenses sharp. Training staff in best practices and fostering a culture of cybersecurity awareness is also key.

Understanding the threats and putting the right defenses in place will significantly mitigate the risks associated with these types of attacks. Remember, in the digital world, security isn’t a one-time task. It’s an ongoing commitment. Remaining vigilant can help you stay one step ahead of potential threats.

Learn more about AD security

New Attack Paths? AS Requested Service Tickets

Active Directory Change Auditing & Rollback

Resource Hub: AD Security 101, From the Front Lines

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