Microsoft Zerologon Flaw Under Attack By Iranian Nation-State Actors

Microsoft is warning that an Iranian nation-state actor is now actively exploiting the Zerologon vulnerability (CVE-2020-1472), adding fuel to the fire as the severe flaw continues to plague businesses.

The advanced persistent threat (APT) actor, which Microsoft calls MERCURY (also known as MuddyWater, Static Kitten and Seedworm) has historically targeted government victims in the Middle East to exfiltrate data. Exploiting the bug allows an unauthenticated attacker, with network access to a domain controller, to completely compromise all Active Directory identity services, according to Microsoft.

“MSTIC has observed activity by the nation-state actor MERCURY using the CVE-2020-1472 exploit (Zerologon) in active campaigns over the last 2 weeks,” according to a Microsoft tweet on Monday evening.

Microsoft released a patch for the Zerologon vulnerability (CVE-2020-1472) as part of its August 11, 2020 Patch Tuesday security updates.  The bug is located in a core authentication component of Active Directory within the Windows Server OS and the Microsoft Windows Netlogon Remote Protocol (MS-NRPC). As previous reported, the flaw stems from the Netlogon Remote Protocol, available on Windows domain controllers, which is used for various tasks related to user and machine authentication.

Then, earlier in September, the stakes got higher for risks tied to the bug when four public proof-of-concept exploits for the flaw were released on Github. This spurred the Secretary of Homeland Security to issue a rare emergency directive, ordering federal agencies to patch their Windows Servers against the flaw by Sept. 21.

Microsoft’s alert also comes a week after Cisco Talos researchers warned of a spike in exploitation attempts against Zerologon.

MSTIC has observed activity by the nation-state actor MERCURY using the CVE-2020-1472 exploit (ZeroLogon) in active campaigns over the last 2 weeks. We strongly recommend patching. Microsoft 365 Defender customers can also refer to these detections: https://t.co/ieBj2dox78

— Microsoft Security Intelligence (@MsftSecIntel) October 5, 2020

Microsoft did not reveal further details of the MERCURY active exploitations in terms of victimology; however, a graph on its website shows that exploitation attempts (by attackers and red teams in general) started as early as Sept. 13 and have been ongoing ever since.

“One of the adversaries noticed by our analysts was interesting because the attacker leveraged an older vulnerability for SharePoint (CVE-2019-0604) to exploit remotely unpatched servers (typically Windows Server 2008 and Windows Server 2012) and then implant a web shell to gain persistent access and code execution,” said Microsoft in an earlier analysis. “Following the web shell installation, this attacker quickly deployed a Cobalt Strike-based payload and immediately started exploring the network perimeter and targeting domain controllers found with the Zerologon exploit.”

Microsoft for its part is addressing the vulnerability in a phased rollout. The initial deployment phase started with Windows updates being released on August 11, 2020, while the second phase, planned for the first quarter of 2021, will be an “enforcement phase.”

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