Active Directory (Part 12.2)

By Ashwin Venugopal -

 






Exploitation

Several methods can be used to exploit misconfiguration in an Active Directory environment. Such methods includes AD delegation, forcing authentication relays, targeting AD users, domain trusts, and using Group Policy Objects or Silver and Golden Tickets. Other methods can also be used according to the AD environment.

Automated Relays- They allow authentication credentials to be forwarded or "relayed" from one system to another. These relays can be established via various protocols and techniques like SMB, NTLM, Kerberos, and others. A penetration tester can use automated relays to capture and use credentials to gain unauthorized access to sensitive information or resources within the AD environment. 

Printer bug is a vulnerability that affects certain versions of the Microsoft Windows operating systems. It allows an attacker to remotely execute arbitrary code on a system by sending a specially crafted print job to a printer that is shared on the network. So, in an AD environment, this bug can be potentially used to gain unauthorized access to sensitive information or resources. However, to exploit this, apart from machine account administrative privileges, there are also another four conditions that should be met:

  1. A valid set of AD account credentials.
  2. Network connectivity to the target's SMB service.
  3. The target host must be running the Print Spooler service.
  4. The hosts must not have SMB signing enforced.

Also, to relay the forced authentication attempt through SMB, it is necessary to disable the enforcement of SMB signing. By default, the SMB signing is allowed but not enforced, i.e., it will only be used if supported. However, if a malicious SMB server is set up, it is possible to disable support for SMB signing, forcing the target system not to sign the SMB authentication attempt during the relay process. 

AD Users- Habits and practices of users (like having weak passwords or offering excessive permissions), sometimes make them the weakest link in an organization's security chain.  Hence, this aspect is also important to consider while attacking an AD environment. Credential management is beneficial because users may have multiple sets of credentials and may struggle to remember all of them. Keylogging can be a useful tool for attackers to understand how normal users interact with a system, along with screen captures. 

GPOs- A GPO is a virtual collection of policy settings. Each GPO has a unique name, called GUID. each Windows computer has a Local Policy Configuration containing several notable configurations like: 
  1. Application configuration for services like the Firewall, Anti-Virus, and Applocker. 
  2. Local Group membership such as the Administrator or Remote Desktop Users groups.
  3. Startup configuration like scripts should be executed.
  4. Security and protocol settings such as SMBv1 support. 
Although there are several ways in which GPOs can be exploited, but if the penetration tester has an AD account he controls that is both local Administrator and local Remote Desktop User, then, it will allow him administrative privileges on a machine and the ability to RDP in. To modify the GPO, the tester will have to access Group Policy Management as the AD user having relevant permissions. 

Conclusion

This part discovers more exploitation methods in an AD environment. 












































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