Active Directory (Part 9)

By Ashwin Venugopal -

 




Microsoft Deployment Toolkit

The Microsoft Deployment Toolkit (MDT) is a service of Microsoft that can automate the deployment of Microsoft Operating Systems (OS) in large organizations. It helps the organizations to efficiently deploy new images across their IT infrastructure, as the base images can be stored and maintained in a central location. It helps in streamlining the deployment process, ensuring the smooth running of the most up-to-date versions of the OS.

Generally, MDT is used with Microsoft's SCCM, which is a tool for managing updates for all Microsoft applications, services, and operating systems. MDT is designed such that it can easily deploy new images, allowing the IT staff to preconfigure and manage boot images. Hence, even if a new device is added to the network, it will be automatically configured with necessary software settings by simply connecting it to the network. 

The SCCM is like an extension to the MDT. However, SCCM is responsible for managing updates and patches for all software installed across the organization's IT infrastructure. It helps the IT staff in reviewing the available updates and test them in a sandbox environment before deploying them centrally to all domain-joined devices. 

But, tools like SCCM and MDT that offers centralized management of IT infrastructure, can also be targeted by the attackers who seek to take control of large amount portions of the organization's critical functions. So, it is important to secure these tools ad properly configure them to prevent unauthorized access or exploitation by the attackers. 

The most common feature used by the organizations is PXE boot. It allows the new devices that are connected to the network to load and install the OS over a network connection. the communication flow between the different components involved in the PXE boot process would be:

  1. User sends DHCP Discover (requests IP address and PXE service info)
  2. Server sends DHCP Offer (sends open IP and PXE service info)
  3. User sends DHCP Request (accepts IP address)
  4. Server sends DHCP Acknowledge
  5. Client performs Boot Service Discover
  6. Server Acknowledge (sends PXE boot information)
  7. Client requests PXE Boot via TFTP
  8. Server delivers PXE Boot via TFTP 

Once the process is performed, the client will use a TFTP connection to download the PXE boot image. The penetration tester can then be able to exploit the PXE boot image for following purposes:

  • Inject a privilege escalation vector, such as a Local Administrator account, to gain Administrative access to the OS once the PXE boot has been completed.

  • Perform password scraping attacks to recover AD credentials used during the install.

Configuration Files

Configuration Files are an excellent avenue to explore while recovering AD credentials. According to the breached host, various configuration files may be of value for enumeration-
  1. Web application config files
  2. Service configuration files
  3. Registry keys
  4. Centrally deployed applications
A penetration tester and an attacker may acquire credentials from a centrally deployed application like a database. A tool called splitebrowser can help the attacker in opening and reading the database. This one of the many potential ways a penetration tester can get hold of AD credentials of some users.  

Various steps that an organization can take to mitigate the risk of attacks on the Active Directory environment are as follows: 

  • User awareness and training- Training users to be aware of potential threats and to be cautious about disclosing sensitive information, like login credentials, will reduce the risk of an attack.

  • Limiting the exposure of AD services and applications online- Many services and applications, like NTLM and LDAP authentication, need not to be accessed via internet. They can be placed in an intranet environment that can be accessed through VPN (Virtual Private Network), providing additional security through the use of multi-factor authentication.

  • Enforcing Network Access Control (NAC)- It can prevent attackers from connecting rogue devices to the network. But, it might require extra efforts to allow the listing of legitimate devices.

  • Enforcing SMB signing- It can help prevent SMB relay attacks. 

  • Following the principle of least privilege- Following this rule especially for the credentials used for services, will reduce the risk of their compromise to a large extent. 

The above measures will help an organization in protecting their AD environment from potential attacks.

Conclusion

Here, we discussed about Microsoft deployment toolkit and preventive measures to reduce risk of compromise of AD environment.






















































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