Storm-0501 and Windows Defender: How Your Coverage Gaps Can Leave a Window Open for Hackers

Threat group Storm-0501 recently used incomplete Windows Defender coverage to facilitate a cloud based ransomware attack . This blog post discusses the dangers of incomplete coverage, and how you can deploy the Nagomi platform to check for converge gaps

We’ve all heard it: attackers evolve faster than defenses. Last week, Microsoft Threat Intelligence showed us exactly what that looks like, highlighting how threat group Storm-0501 is shifting its playbook.

Instead of sticking to on-prem ransomware, the group has started moving to cloud-based ransomware deployment. The reason? Incomplete Windows Defender coverage left the door wide open.

At Nagomi, this is exactly the kind of risk we help customers get ahead of. Because when attackers pivot, security teams need a clear view of where defenses are thin and how to close the gaps before they’re exploited.

Storm-O501: What You Need to Know

Storm-0501 is a financially motivated cybercriminal group, active since 2021. The group initially targeted U.S. school districts with the Sabbath ransomware before shifting to a ransomware-as-a-service (RaaS) model, deploying multiple ransomware strains, including Embargo. Their tactics include credential theft, exploiting vulnerabilities, and using tools such as Cobalt Strike and Rclone for lateral movement and data exfiltration.

The group has specifically targeted U.S. sectors including government, manufacturing, transportation, and law enforcement.

How Does Storm-0501 Operate?

The group usually starts by exploiting weak or over-privileged accounts. From there, they move from on-prem endpoints into cloud environments, set up backdoor access, and then launch ransomware.

But what makes their recent campaign different is how they used cloud-native features instead of traditional malware. That allowed them to:

• Exfiltrate massive amounts of data
• Delete backups and critical files
• Issue ransom demands with higher odds of success

In one case, they compromised a large enterprise with multiple subsidiaries. The weak link? Defender for Endpoint was only deployed in one Azure tenant. Other subsidiaries and domains weren’t consistently covered, creating blind spots. Once Storm-0501 gained a foothold, they authenticated as a Global Admin and pivoted into Azure, stealing data and wiping backups.

What This Means for Security Teams

This is a textbook example of how coverage gaps can undermine even the most advanced defenses. If your endpoint protection isn’t applied consistently across every tenant, domain, and device, attackers will find the cracks.

That’s where Nagomi helps. With our Coverage Rules, teams can spot those inconsistencies before attackers do. We integrate across dozens of tools, cross-referencing data to flag gaps in EDR deployments like Microsoft Defender. Even better, coverage rules can be customized so each subsidiary or business unit gets protection tailored to its environment.

Answers in Three Simple Steps

1. Log into your Nagomi Platform and click “Summary” from the left menu. From here, click “Coverage” on the top left hand slide of the screen.
2. This page provides teams with a high-level overview of your organization’s Microsoft Defender coverage, identifying the percentage of devices which are currently covered and which are not, allowing you to understand the scope and severity of any potential gaps, and begin developing a plan in order to close these gaps.
3. Download a CSV from the Nagomi platform the list of assets which don’t have Defender deployed, and/or create a ticket directly with Microsoft Defender to deploy across the identified assets.

Take a quick walk through

Storm-0501 is one name on a long list of threat groups, but the actors themselves aren’t the point. What matters is how exposed your environment is when coverage gaps exist. Closing those gaps quickly and consistently is the real defense.

Nagomi makes that possible by surfacing blind spots and guiding teams to act where it counts. The organizations that stay safe don’t wait for the next campaign to make headlines, they get ahead of it and defend proactively.

If you’re ready to close the gaps, we’ll show you how. Let us walk you through real examples from environments like yours.

Watch our walkthrough or request a demo to see how we help teams surface what matters, skip the noise, and finally prove they’re protected.