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Pass-the-Hash Is Dead? Not Quite: Mitigation of PtH Attacks

Despite claims to the contrary, Pass-the-Hash (PtH) attacks are still a significant threat in cybersecurity. While there have been strides in mitigating these attacks, especially in Windows environments, they remain a viable technique for attackers.


Current Status of PtH Attacks

Despite advancements in security, PtH attacks are far from obsolete. They are particularly effective in Windows Active Directory environments. Attackers who obtain password hashes from a domain can use these hashes to move laterally within the network, accessing other domain members without needing the plaintext passwords.


Key Mitigations and Improvements

Microsoft has taken significant steps to mitigate the risk associated with PtH attacks:

Windows Defender Credential Guard

  • Windows Defender Credential Guard uses virtualization-based security to isolate credentials from the main operating system. This makes it more challenging for attackers to access and exploit password hashes.

  • Learn more about Credential Guard here.


Registry Key: LocalAccountTokenFilterPolicy

  • This registry key plays a crucial role in PtH attack prevention for systems not attached to a domain.

  • By default, the value is set to 0, which disables PtH and remote command execution for all users except the built-in Administrator (RID 500) account: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LocalAccountTokenFilterPolicy


  • When set to 0, remote users cannot execute commands on the target system using either plaintext passwords or password hashes. This mitigates PtH attacks effectively, as the built-in Administrator account is typically disabled on local Windows systems.

  • Many organizations change this value to 1, re-enabling PtH attacks for all accounts on the system. This setting should be avoided unless absolutely necessary.

Stronger Hash Retrieval Prevention

  • Upgrades to Windows 10 and beyond have made it more difficult to retrieve password hashes, particularly with the introduction of mitigations against tools like Mimikatz that previously made hash retrieval straightforward.


Conclusion

Pass-the-Hash attacks continue to be a potent threat in modern IT environments, especially within Windows Active Directory networks. By understanding the mechanisms of PtH attacks and implementing robust security measures, organizations can significantly reduce their risk and protect their digital assets. While the battle against PtH is ongoing, staying informed and vigilant is the key to maintaining a secure environment.


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