CISA has released guidance aimed at helping government agencies and enterprises enhance their cybersecurity operations by using expanded cloud logs in Microsoft 365 tenants. These expanded capabilities, introduced under Microsoft Purview Audit (Standard), allow organizations to access critical event logs, including information about mail activity, user searches, and other actions within services like Exchange Online and SharePoint Online. These logs are particularly valuable for monitoring and analyzing user and admin operations, helping organizations track critical activities across multiple Microsoft services.
The enhanced logs are expected to bolster threat-hunting capabilities, especially in scenarios such as business email compromise (BEC), advanced nation-state cyberattacks, and insider risks. These new logging features provide additional telemetry that can help detect and investigate suspicious activities. By integrating these logs into Security Information and Event Management (SIEM) systems, including Microsoft Sentinel and Splunk, organizations can more effectively track and respond to potential threats.
The introduction of these expanded logging capabilities came in response to a major cybersecurity breach in 2023.
The introduction of these expanded logging capabilities came in response to a major cybersecurity breach in 2023. In that incident, Chinese hackers, identified as Storm-0558, exploited vulnerabilities in Microsoft’s Exchange Online to steal over 60,000 emails from senior U.S. government officials. The hackers gained access to targeted email accounts using stolen authentication tokens, which were forged from a Windows crash dump. Despite evading detection for a period, the breach was eventually uncovered when the State Department’s Security Operations Center (SOC) used enhanced logging capabilities to identify unusual activity.
Following the breach, Microsoft expanded its free logging capabilities for all Purview Audit Standard customers with E3/G3 licenses and above. Previously, detailed logs such as the MailItemsAccessed event were only available to customers with Purview Audit Premium licenses, which had hindered the ability of organizations to detect the attack earlier. The expanded logging, now available to more customers, provides essential information to help prevent similar incidents in the future and strengthens organizations’ overall cybersecurity posture.
