Microsoft Flags Storm-0940 Use of ARTEX AI Agents in ConnectWise Breach

An AI-driven attack has compromised thousands of cloud tenants after exploiting a software supply chain flaw. Microsoft has disclosed that a China-state-aligned actor, tracked as Storm-0940, utilized an autonomous artificial intelligence framework to breach ConnectWise, a managed service provider platform. This intrusion allowed the group to obtain credentials for a multi-tenant application, which were subsequently used to attempt sign-ins across more than 2,250 Microsoft 365 tenants. In some instances, the attackers achieved privileged access within three hours of their initial targeting.

The operation relied on ARTEX, an open-source framework that utilizes large language model agents to perform penetration testing autonomously. Microsoft described it as a system of LLM-driven agents that run an autonomous penetration test. According to the security vendor, this technology enabled the group to accelerate scanning, reconnaissance, and password spraying activities. The agents function continuously with little required human interaction, operating at a speed that leaves defenders with little time to detect and respond.

The timeline of events began with unauthorized access to the ConnectWise multi-tenant application. Following this access, the group began automated password guessing, specifically targeting 327 accounts across eight organizations. This specific campaign generated more than 151,000 failed logons without any successes. On October 11, the password spray reached a peak intensity of 2,900 attempts per minute, totaling over 111,000 attempts for that day.

While the direct password guessing attempts failed, the attackers possessed stolen application credentials that allowed them to authenticate without a user sign-in. Using four application credentials, the group executed more than 200 sign-ins in under four minutes. These actions were taken from a single IP range. Inside some tenants, operations included Graph and directory activity, reconnaissance, and changes to identities, groups, and privileged roles.

Security firm Huntress observed specific malicious behaviors within a tenant on October 15. An application added itself to the top administrator role, triggering a Microsoft Defender alert regarding an application self-assigned Global Administrator role. Investigators also noted the planting of new secrets scheduled to expire in 2028. By October 16, Huntress confirmed unauthorized sign-ins for 162 tenants, and by October 17, activity was seen in almost 1,000 Entra tenants, with more than 300 succeeding.

Microsoft has confirmed that the activity did not result from a compromise of or a vulnerability in Microsoft’s systems, products, or services. However, the use of ARTEX has been linked to other incidents. Public reporting this month connected the tool to breaches at South Korean financial institutions, and CrowdStrike suggested the suspect in those attacks was likely based in China and used ARTEX with Anthropic’s Claude Code. The developer of ARTEXT, known as Autumn-27, stated on GitHub that the project will no longer be updated and will become closed source.

ConnectWise has suspended Cloud Backup, formerly known as SkyKick, along with SaaS Security and Cloud Management as a precaution. A phased restoration process has begun, with recovery expected to take several days. The company noted it has no indicators to date 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 from this month where logs allow.