ThreatFox: SmartLoader IOCs

Hunt Hypothesis

The ThreatFox: SmartLoader IOCs rule detects potential multi-stage malware activity indicative of SmartLoader, a loader that establishes persistence and exfiltrates data through command-and-control communication. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate advanced persistent threats before they exfiltrate sensitive data or deploy additional payloads.

IOC Summary

Malware Family: SmartLoader Total IOCs: 3 IOC Types: url, ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - SmartLoader
let malicious_ips = dynamic(["89.169.12.235", "89.169.12.149"]);
CommonSecurityLog
| where DestinationIP in (malicious_ips) or SourceIP in (malicious_ips)
| project TimeGenerated, SourceIP, DestinationIP, DestinationPort, DeviceAction, Activity
| order by TimeGenerated desc

KQL: Ip Hunt Device

// Hunt in Defender for Endpoint network events
let malicious_ips = dynamic(["89.169.12.235", "89.169.12.149"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - SmartLoader
let malicious_urls = dynamic(["http://89.169.12.149/api/NTE3YjdjNWU1NjYzNjU2YTA1N2Y="]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — SmartLoader

False Positive Guidance

• Scenario: Scheduled System Maintenance Task
  Description: A legitimate scheduled task runs a script that downloads a file from a known ThreatFox indicator (e.g., a file hash or URL associated with SmartLoader).
  Filter/Exclusion: Check for task scheduler or schtasks.exe in the process tree, and verify if the file is part of a known enterprise maintenance script or tool (e.g., PowerShell scripts used for system updates).

• Scenario: Admin Using Process Hollowing Technique
  Description: An administrator is using process hollowing to deploy a legitimate tool (e.g., PsExec, WMIC, or CertUtil) to execute a script or tool on a remote machine.
  Filter/Exclusion: Filter out processes initiated by admin accounts with runas or PsExec in the command line, and check for known legitimate tools in the execution path.

• Scenario: Software Update via Microsoft Update
  Description: A file hash or URL associated with SmartLoader is mistakenly listed in ThreatFox, and a legitimate Microsoft update file is being downloaded by Windows Update.
  Filter/Exclusion: Filter based on the source IP (e.g., Microsoft’s update servers) or check the file name against known Microsoft update packages (e.g., WindowsUpdate.exe, wuauclt.exe).

• Scenario: Data Exfiltration via Legitimate Cloud Service
  Description: An enterprise application is using a cloud service (e.g., AWS S3, Azure Blob Storage) to transfer data, and the endpoint is flagged as a SmartLoader IOC.
  Filter/Exclusion: Filter by the cloud service provider’s IP ranges or domain names, and verify if the file is part of a known data transfer process (e.g., backup, sync, or reporting tools like AWS CLI, Azure CLI).