Microsoft today warned of continued attack activity exploiting Zerologon (CVE-2020-1472), a critical elevation of privilege flaw affecting the Netlogon protocol. The Department of Homeland Security's Cybersecurity and Infrastructure Security Agency (CISA) has issued an alert to spread awareness of the activity.
Zerologon was patched in August but became a top security concern after discovery of publicly available exploit code. A remote attacker could exploit this vulnerability and breach unpatched Active Directory domain controllers, then obtain domain administrator access.
Earlier this month, Microsoft observed an Iranian advanced persistent threat (APT) group known as Mercury using the vulnerability in active attack campaigns. CISA has also detected nation-state activity exploiting Zerologon that has often, but not exclusively, targeted federal and state, local, tribal, and territorial (SLTT) government networks.
"Deploying the August 11, 2020 security update or later release to every domain controller is the most critical first step toward addressing this vulnerability," Aanchal Gupta, vice president of engineering for the Microsoft Security Response Center (MSRC), writes in a blog post.
"Once fully deployed, Active Directory domain controller and trust accounts will be protected alongside Windows domain-joined machine accounts." He advises businesses to find devices making vulnerable connections by monitoring event logs, and to address noncompliant devices.
CISA urges administrators to patch their domain controllers immediately: "Until every domain controller is updated, the entire infrastructure remains vulnerable, as threat actors can identify and exploit a vulnerable system in minutes," officials write.