2,250 Tenants: The Scale of AI-Driven Intrusion in ConnectWise Breach

The integration of artificial intelligence into offensive cyber operations has moved from theoretical concern to operational reality, forcing security teams to reconsider their detection timelines. Recent disclosures reveal a sophisticated supply chain attack that utilized automated agents to sweep through cloud environments at a speed that traditional monitoring systems struggled to match.

The first key point centers on the sheer volume of the operation. According to Microsoft’s analysis, the threat group, identified as Storm-0940, attempted sign-ins against more than 2,250 distinct Microsoft 365 tenants. These attempts were not random brute-force efforts but were executed using stolen credentials from ConnectWise applications. Because these applications authenticated without interactive user sign-ins, the agents could move through the infrastructure with a level of stealth and speed that bypassed many standard user-based alert triggers.

The second critical element is the speed at which the attackers gained footing. In several instances, the group achieved privileged access less than three hours after initially targeting a specific tenant. This rapid escalation underscores a significant shift in the attack lifecycle. The use of ARTEX, an open-source agentic AI penetration testing framework, allowed the attackers to automate scanning, reconnaissance, and credential abuse. The system operates with minimal human interaction, effectively working around the clock and compressing the window available for defenders to detect anomalies and respond.

The third key aspect involves the methodology of the intrusion, which combined automated password spraying with OAuth application abuse. The attackers targeted 327 accounts across eight organizations, generating over 151,000 failed logon attempts. While nearly 98% of this activity resulted in account lockouts, the success lay in the control of multiple ConnectWise cloud app identities. Using just four application credentials, the agents executed more than 200 sign-ins within a four-minute window from the same IP range, demonstrating a highly efficient, scripted approach to tenant traversal.

Contextualizing the threat actor, Storm-0940 is described as a China-state-aligned group active since 2021, with no known industry aliases. The campaign targeted 14 industries, including aerospace, defense, semiconductors, government, and think tanks. Microsoft clarified that the breach did not stem from a vulnerability in its own systems but rather from unauthorized access to the multi-tenant ConnectWise application. This distinction is crucial for understanding the supply chain dynamics, where a single compromised service provider can expose a vast network of downstream customers.

The operational details further highlight the sophistication of the attack. On October 11, the password spraying activity peaked at 2,900 attempts per minute. In one specific tenant, security firm Huntress observed an application adding itself to the top administrator role, a behavior that triggered a specific alert in Microsoft Defender. The attackers also planted new secrets set to expire in 2028, suggesting an intent to maintain long-term access. By October 16, Huntress had confirmed unauthorized sign-ins for 162 tenants, a number that swelled to nearly 1,000 by the following day, with more than 300 sign-ins succeeding.

The use of ARTEX marks a departure from traditional attack patterns. The framework, which can utilize any AI model, has been linked to other breaches, including those at South Korean financial institutions. The developer of ARTEX, known by the handle “Autumn-27,” announced on GitHub that the project would become closed source and cease updates. This move may signal an attempt to consolidate control over the tooling or to limit its widespread availability to other threat actors, though the tool’s impact is already evident in the current campaign.

In response, ConnectWise suspended several of its services, including Cloud Backup and SaaS Security, as a precautionary measure. The company has begun a phased restoration process, with recovery expected to take several days. Currently, there are no indicators that partner backup data was compromised. Microsoft advises customers to keep affected app connections disabled until formal restoration instructions are issued and to review activity logs from this month where possible. The incident serves as a stark reminder that while a successful sign-in does not guarantee data exfiltration, the speed of AI-driven attacks leaves little room for error in defensive postures.