China-aligned hackers used an AI pentest tool against more than 2,250 Microsoft 365 tenants after a ConnectWise breach

Microsoft says a China state aligned hacking group it tracks as Storm-0940 used an agentic AI penetration testing framework to break into organizations at machine speed, and that the group was behind the recently disclosed compromise of ConnectWise, the IT management and remote access company.

According to Microsoft, the attackers broke into ConnectWise's cloud backup service and stole application credentials that link ConnectWise to its corporate customers. With those credentials, they could sign in to customers' Microsoft hosted environments as if they were an authorized app and reach email and files. Microsoft says they used ARTEX, an open source AI framework built to stress test defenses, to go after about 2,250 organizations at nearly 3,000 sign-in attempts per minute. In several cases, the time from first targeting to privileged access to a victim's cloud was under three hours. Microsoft said the speed leaves defenders "little time to detect and respond."

The activity dates back to at least September 2026 and hit organizations across many industries. Reports say the same framework was used in a recent compromise of South Korean financial systems, many of which had weak security and lacked multi-factor authentication. ConnectWise says it paused access to the affected cloud backup system and has no evidence that its encrypted backup archives were accessed.

Microsoft's point is that agents are not limited by human constraints. They work around the clock and try many breach paths at once, which compresses the time between picking a target and reaching it.

Why it matters for builders: this is a concrete case of offensive AI tooling scaling a supply chain attack. Third party app credentials and OAuth grants into Microsoft 365 or Google Workspace are now a high value target, and rate based detection has to assume attackers can move far faster than a person.

What to do: audit which third party apps hold standing access to your tenant, rotate their secrets, enforce MFA and conditional access everywhere, and alert on bursts of app sign-ins.

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