On September 11, 2020, detailed technical information was made public regarding a critical Microsoft Windows vulnerability (CVSS 10) that was included in Microsoft's August 2020 Patch Tuesday set of updates and appears to affect all currently supported Windows Server (2008 R2 and above).
When originally disclosed in August, the vulnerability was given the official designation of CVE-2020-1472 , but not much detail on the vulnerability itself was made public.
However, we know that this vulnerability, now dubbed "Zerologon," may allow an attacker to take advantage of the cryptographic algorithm used in the Netlogon authentication process and impersonate the identity of any computer when trying to authenticate against the domain controller. From there, a variety of other attacks, including but not limited to disabling security features, changing passwords, and essentially taking over the domain are possible.
The entire attack as demonstrated, is very fast, and can be executed in approximately 3 seconds, so it could be very dangerous. In addition, Trend Micro is now aware of weaponized proof-of-concept code that has been made publicly available, meaning that real exploits could be close behind.
Mitigation and Protection
First and foremost, the first line of protection against this vulnerability is to ensure that all affected systems are patched with Microsoft's latest security update. This continues to be the primary recommendation for protection against any exploit that that may arise from this vulnerability.
According to the research, there is one serious limitation to exploits of this vulnerability - specifically it cannot be exploited remotely. An attacker will first need to gain access to the network domain via other means (legitimately or not). So one major mitigation point would be to ensure that network access (both physical and remote) are carefully guarded. However, if an attacker has obtained access to a network via another vulnerability or legitimately, this could become a powerful exploit.
Trend Micro Protection
To assist customers, Trend Micro has created and released some additional layers of protection in the form of Deep Security and Cloud One - Workload Security IPS rules and TippingPoint filters that may help organizations strengthen their overall security posture, especially in situations where comprehensive patching may take time or is not feasible.
Deep Security and Cloud One - Workload Security, Vulnerability Protection and Apex One Vulnerability Protection (iVP)
- Rule 1010519 - Microsoft Windows Netlogon Elevation of Privilege Vulnerability (CVE-2020-1472)
- Rule 1010521 - Microsoft Windows Netlogon Elevation of Privilege Vulnerability Over SMB (CVE-2020-1472)
- Filter 38166: MS-NRPC: Microsoft Windows Netlogon Zerologon Authentication Bypass Attempt
Trend Micro is continuing to aggressively look into other forms of detection and protection to assist our customers, but we do want to continue to reiterate that the primary recommendation is to apply the official Microsoft patches as soon as possible. We will continue to update this article and our customers if/when additional layers of protection are found.
- Trend Micro Blog: Zerologon” and the Value of Virtual Patching - https://www.trendmicro.com/en_us/research/20/i/zerologon-and-value-of-virtual-patching.html
- Trend Micro Video (Youtube) - Cloud One - Workload Security about Zerologon
- Microsoft Advisory - https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472