ThreatFox: Stealc IOCs

Hunt Hypothesis

This detection rule identifies adversary activity associated with the Stealc malware by monitoring specific Indicators of Compromise (IOCs) known to facilitate data theft and lateral movement within cloud environments. Proactively hunting for these IOCs in Azure Sentinel is critical because early identification of Stealc infections allows the SOC team to rapidly isolate compromised assets before sensitive data exfiltration or broader network propagation occurs.

IOC Summary

Malware Family: Stealc Total IOCs: 2 IOC Types: ip:port, url

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Stealc
let malicious_ips = dynamic(["193.148.56.206"]);
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(["193.148.56.206"]);
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 - Stealc
let malicious_urls = dynamic(["http://193.148.56.206/"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Stealc

False Positive Guidance

Here are specific false positive scenarios and corresponding filters for the ThreatFox: Stealc IOCs detection rule in an enterprise environment:

• Scenario: Scheduled Antivirus or EDR Definition Updates

  • Context: Enterprise endpoints running tools like CrowdStrike Falcon, Microsoft Defender for Endpoint, or Symantec Endpoint Protection often trigger background processes that download and install signature updates. These processes may generate network traffic or file hashes matching Stealc’s known IOCs (specifically specific DLLs or update executables) due to shared vendor libraries or similar naming conventions.
  • Suggested Filter/Exclusion: Create an exclusion rule based on the Process Name and Parent Process. Exclude alerts where the parent process is C:\Program Files\Microsoft Defender\MpCmdRun.exe (for Defender) or C:\ProgramData\CrowdStrike\FalconSensor\csfalcon.exe, provided the file path of the triggered IOC matches the vendor’s standard installation directory.

• Scenario: Legacy Internal Deployment Tool Execution

  • Context: IT Operations teams frequently utilize internal deployment agents (e.g., Microsoft System Center Configuration Manager (SCCM) or Ivanti Neurons) to push software patches or configuration scripts. These tools often execute PowerShell scripts or batch files that instantiate temporary processes with hashes identical to Stealc’s IOCs, particularly if the organization uses a shared library of internal utilities that coincidentally matches the threat signature.
  • Suggested Filter/Exclusion: Implement a filter excluding events where the User Account is a known service account (e.g., DOMAIN\SCCM-Deploy-Svc or DOMAIN\Admin-Patch) and the Process Path resides within the internal deployment directory (e.g., C:\Program Files\SMS_CCM\).

• Scenario: Automated Backup and Archiving Jobs