Microsoft assesses the group was behind the recently disclosed ConnectWise supply chain compromise of a multi-tenant cloud backup application.
In some cases, the group went from first targeting an organization to privileged access to its cloud infrastructure in under three hours.
Microsoft said the activity did not stem from a compromise of, or vulnerability in, its own systems, products, or services.
Microsoft notes that agents can work around the clock and try several breach paths at once.
After the ConnectWise intrusion, the group used ARTEX to attempt sign-ins to more than 2,250 tenants (separate customer environments) at up to 2,900 attempts per minute, leaving defenders little time to respond.
Most of the targeting failed, but Microsoft says the group still gained lasting privileged cloud access at many organizations.
Between October 10 and 14, 2026, infrastructure tied to the group ran a password-spray campaign against 327 accounts at eight organizations, producing more than 151,000 failed logons, with no successful authentication observed.
Microsoft says that infrastructure matches network addresses in ConnectWise's advisory, including one identical IP address.
Microsoft says the attackers abused stolen credentials of ConnectWise cloud applications that customers had already trusted, which let them sign in to Microsoft 365 environments without an interactive user login. In multiple environments, they then used Microsoft Graph, the interface for Microsoft 365 data and directory settings, for reconnaissance, application credential changes, and attempts to alter privileges. Such changes can work as a backdoor even after the original application is fixed. Microsoft stresses that an affected application or a successful sign-in does not necessarily mean data was accessed or stolen. It advises customers to keep affected ConnectWise connections disabled until ConnectWise gives restoration instructions, preserve evidence, review service principal sign-ins and credential or privilege changes, and follow ConnectWise's containment guidance. Microsoft Defender XDR offers detections and hunting queries for the activity.