IOTW: Despite Patch, Zerologon Attack Still A Big Deal

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Seth Adler
10/23/2020

A known Windows vulnerability is detected alive and well thanks to one man’s honeypot experiment.

Facts

Security vulnerability CVE-2020-1472, which was discovered and patched earlier this year, is still running rampant. Dubbed Zerologon, it is unique in its simplicity. It works by exploiting a Netlogon weakness. Netlogon is the always-on Windows service that enables end users to log into a network. The scripted hack runs incredibly quickly, searching for unpatched Active Directory systems and exploiting a weakness by adding the number zero in certain Netlogon authentication fields.

On October 16, a month after Microsoft released its first patch, independent researcher Kevin Beaumont drew the hack out by utilizing a honeypot he maintains to detect threats. Honeypots work by intentionally setting up vulnerabilities in order to bait and identify cyber security threats. Using an unpatched lure server, Beaumont discovered that hackers were able to backdoor the server by changing an admin password. From there, hackers have access to domain controllers that administrators use to create and manage accounts across an organization. The hacker can then impersonate any computer connected to the affected network, disable Netlogon security features, and change a network computer’s password.

The attack can only happen once inside a network. However, several noteworthy footholds include firewall and VPN vulnerabilities as well as third-party access through known issues with Citrix, Juniper, and Pulse Secure. Insider threats and phishing schemes can also leverage Zerologon in order to quickly infect an entire enterprise network. Once inside, hackers can deploy ransomware, steal data, commit espionage and other nefarious deeds.

Microsoft released the first patch in August 2020, but it wasn’t without its issues. It involved modifying billions of devices connected to corporate networks which temporarily paused enterprise operations. The temporary fix simply forces Netlogon security features on so the Zerologon attack can’t turn them off to sneak inside.

A more robust patch is scheduled to release in February of 2021. However, Microsoft predicts the new patch will permanently disable standing authentication procedures on some devices.

Related: Patchwork Of Privilege

The Cybersecurity and Infrastructure Security Agency (CISA) warned that Zerologon targets include government networks, potentially affecting election related networks. Their statement released on October 16 reads in part, “Although it does not appear these targets are being selected because of their proximity to elections information, there may be some risk to elections information housed on government networks.

CISA is aware of some instances where this activity resulted in unauthorized access to elections support systems; however, CISA has no evidence to date that integrity of elections data has been compromised.”

Quick Tips

In theory, threats like Zerologon should never pose much of a problem. After the initial discovery, a patch is made and released as a Windows update. Once the update is installed, the network is secure.

In practice, however, updates don’t always happen with any sort of urgency. Especially in the case of the Zerologon patch, its time-consuming nature may prompt careless employees to bypass updates in order to keep their system up and running. Certain organizations may decide that the downtime involved in their 24/7 operation is too costly for a fix that may never threaten them in the first place. Some networks are running on servers that will no longer be supported as of November 2020, meaning that, although they will have received the first patch, the second patch won’t automatically install.

Related: Developing A Culture Of Enterprise Cyber Security Resilience

These are simple fixes for a holistic IT team and a solid cyber security framework—for enterprises that have one. Additional mitigation measures include:

  • Applying the Microsoft patch ASAP
  • Using a relevant script or third-party cyber security team to ensure that all domain controllers are patched.
  • Monitoring for Group Policy Object (GPO) changes.
  • Enacting a least privilege access policy to minimize internal threats

Read More: Incident Of The Week

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