Red Teaming — AD Enumeration (GPO & ACL)

This is the continuation of the following blog:

• https://medium.com/@gowthamaraj-rajendran/red-teaming-ad-enumeration-domain-objects-trust-2144e7c28939

GPO

GPO, or Group Policy Object, is a powerful feature in Active Directory that allows administrators to manage and configure Windows settings for a group of computers or users. However, from a red teaming perspective, GPO can be a valuable tool for attackers to achieve their goals.

Attackers can use GPO to perform several actions, including:

1. Disabling security features: GPO can be used to disable certain security features, such as Windows Defender, firewall rules, and user account control. By doing so, attackers can easily execute their malicious payloads without being detected.
2. Adding malicious scripts: Attackers can use GPO to add malicious scripts to the startup or logon scripts of the targeted computers. This can allow them to achieve persistence and maintain control over the compromised systems.
3. Escalating privileges: GPO can be used to escalate privileges by configuring the target systems to give the attacker administrative privileges. This can allow them to access sensitive data or perform critical actions that would otherwise be restricted.
4. Creating backdoors: GPO can be used to create a backdoor by configuring the target systems to connect to a command and control server controlled by the attacker. This can allow them to remotely access the compromised systems and perform additional malicious activities.

To protect against these types of attacks, it’s important for organizations to implement strong security measures, such as:

1. Limiting access to GPO: Administrators should limit access to GPO to only authorized personnel who need it to perform their job duties.
2. Implementing auditing and monitoring: Organizations should monitor GPO changes and log activities related to GPO configuration changes. This can help detect any unauthorized changes and suspicious activity.
3. Implementing security baselines: Organizations should implement security baselines to ensure that GPO settings are configured securely and consistently across all systems.

Enumeration

1. Get-NetGPO

Get GPO in the domain.

Other commands:

Get-NetGPOGroup, Find-GPOLocation

2. Get-NetOU

Get OUs in a domain

ACL

Access Control Lists (ACLs) in Active Directory (AD) are a crucial component of securing an organization’s IT infrastructure. From a red teaming perspective, understanding how ACLs work and how to bypass them can be a critical skill for identifying and exploiting vulnerabilities in an AD environment.

ACLs are used in AD to control access to various resources, such as files, folders, printers, and network shares. These permissions are defined at the object level and can be set for individual users, groups, or computers. ACLs consist of access control entries (ACEs), which define who can perform specific actions, such as reading, writing, modifying, or executing a resource.

Red teamers often target ACLs as a way to gain unauthorized access to sensitive data or elevate privileges within an AD environment. One common technique is to identify misconfigured ACLs that grant excessive or unnecessary permissions to users or groups. For example, a red teamer may search for folders or files that have been set to allow Everyone or Authenticated Users full control, which would allow any user to read, write, or modify those resources.

Another tactic is to exploit the way that ACLs are inherited in AD. When a folder or file is created, it inherits the permissions of its parent object by default. However, this can lead to unintended consequences if the parent object has insecure ACLs. Red teamers can leverage this inheritance feature to gain access to resources that they would not otherwise be able to access. For example, if a red teamer gains access to a folder that contains a sensitive file, they may be able to modify the ACLs on that file to grant themselves or another user full control.

Red teamers may also try to bypass ACLs by using various techniques such as abusing default file system permissions or impersonating trusted users. For instance, if a red teamer finds a folder that has a vulnerable ACL, they may try to impersonate a trusted user who has access to that folder to gain entry. They could also look for opportunities to abuse default permissions, such as the ability to execute arbitrary code or scripts from a certain location.

In conclusion, ACLs are an essential security feature in AD, but they can also be a vulnerability if not configured correctly. Red teamers must understand how ACLs work and how to exploit them to identify potential weaknesses in an AD environment. By doing so, they can help organizations improve their security posture and protect against real-world attacks.

Enumeration

1. Get-ObjectAcl

Get the ACLs associated with the specified object

2. Invoke-ACLScanner

Search for interesting ACEs

Conclusion

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In managing and securing Active Directory environments, the process of AD enumeration is crucial. By performing a comprehensive enumeration, organizations can effectively evaluate the users, groups, and resources within their AD infrastructure, facilitating better access control management, activity monitoring, and identification of potential security threats. Different enumeration techniques like LDAP queries and PowerShell scripts allow administrators to gain visibility into their AD environment and ensure it’s well-configured and secured. However, it is vital to exercise caution during enumeration to avoid exposing sensitive information unintentionally. AD enumeration is a critical aspect of AD management and security that requires a regular implementation to maintain a secure and efficiently managed environment.