Since the patch was released in August for Zerologon (CVE-2020-1472), technical details have been made public that allow hackers to use public exploits to attack. Microsoft has detected Zerologon vulnerability being actively exploited on live systems. 
Technically speaking, Zerologon is an authentication bypass in Netlogon Remote Protocol (MS-NRPC) that WIndows uses to authenticate entities in a domain-based environment. Essentially, an internal part of Windows machines authenticating to each other. One of the features of MS-NRPC is that it permits authenticated computers to change their password.
The Zerologon allows a malicious actor to impersonate any computer in the Windows network environment, including the password of the domain controller, and change the domain password. The result is that the attacker gains administrative rights to the Windows domain controller, and takes over the network.
While Zerologon was initially rated ‘Critical’ by Microsoft, the risk posed was later rated as ‘Unlikely’. This vulnerability does not allow an attacker to break into a Windows network, but is an excellent second phase attack to allow lateral movement.
A detailed technical breakdown of the attack is available here.
Th Zerologon patch is a phased release, as the fix affects low-level components and is expected to complete in Q1 2021. It is presently available for supported versions of Windows Server. A company called 0patch has reverse engineered Microsoft’s patch, and developed a version that can be applied to Windows Server 2008 R2 without Extended Security Updates for their paying customers.
Agilient recommends organisations subscribe to threat intelligence services such as Agilient’s partner, Looking Glass Scout Prime, to get notice of similar threats to business continuity. Contact Agilient to discuss your organisation’s cybersecurity.
Author: David Steele, Agilient Consultant