ThreatFox: ACR Stealer IOCs

Hunt Hypothesis

This hunt targets adversary behavior involving the execution of known ACR Stealer indicators to detect active credential theft and data exfiltration attempts within the environment. Proactively searching for these specific IOCs in Azure Sentinel is critical because early identification allows the SOC team to isolate compromised assets before sensitive access tokens are fully harvested by the threat actor.

IOC Summary

Malware Family: ACR Stealer Total IOCs: 3 IOC Types: domain

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - ACR Stealer
let malicious_domains = dynamic(["gw.portallbridge.cc", "operationsframework.cc", "account.operationsframework.cc"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

Required Data Sources

References

• ThreatFox — ACR Stealer

False Positive Guidance

Here are 4 specific false positive scenarios for the ThreatFox: ACR Stealer IOCs detection rule in an enterprise environment, along with suggested filters or exclusions:

• Antivirus Definition Updates via Scheduled Tasks

  • Scenario: The organization uses a third-party EDR (e.g., CrowdStrike Falcon or SentinelOne) that performs nightly definition updates. These updates often involve downloading and executing signed binaries from the vendor’s cloud infrastructure, which may share IP ranges or hash signatures with known ACR Stealer distribution points.
  • Filter/Exclusion: Create an exclusion for processes initiated by the specific EDR service account (e.g., SYSTEM or NT AUTHORITY\Network Service) and filter out network connections originating from the vendor’s trusted update IP ranges documented in their public trust list.

• Enterprise Software Deployment via SCCM/Intune

  • Scenario: The IT Operations team deploys a new version of a productivity suite (e.g., Microsoft Office 365 or Adobe Creative Cloud) using Microsoft Endpoint Configuration Manager (SCCM). The deployment agent (ccmexec.exe) downloads installation packages from the vendor’s content distribution network, which may contain IOCs matching ACR Stealer’s command-and-control infrastructure.
  • Filter/Exclusion: Exclude traffic and process execution where the parent process is ccmexec.exe or Microsoft.IntuneManagementService.exe, specifically when the destination domain matches known enterprise software vendor domains (e.g., *.office.com, *.adobe.io).

• Automated Backup and Synchronization Jobs

  • Scenario: A scheduled backup job using Veeam Backup & Replication or Acronis Cyber Protect runs during off-hours. These tools frequently connect to cloud storage gateways (e.g., AWS S3, Azure Blob) for data replication. The IOCs associated with