Results of Major Technical Investigations for Storm-0558 Key Acquisition

On July 11, 2023, Microsoft published a blog post which details how the China-Based threat actor, Storm-0558, used an acquired Microsoft account (MSA) consumer key to forge tokens to access OWA and Outlook.com. Upon identifying that the threat actor had acquired the consumer key, Microsoft performed a comprehensive technical investigation into the acquisition of the Microsoft account consumer signing key, including how it was used to access enterprise email.