ThreatFox: Stealc IOCs

Hunt Hypothesis

This detection rule identifies adversary activity consistent with the Stealc malware family by monitoring for four specific Indicators of Compromise (IOCs) known to facilitate credential theft and lateral movement. The SOC team should proactively hunt for these signals in Azure Sentinel because early identification of Stealc IOCs allows for rapid containment before attackers can exfiltrate sensitive data or establish persistent backdoors within the cloud environment.

IOC Summary

Malware Family: Stealc Total IOCs: 4 IOC Types: url, ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Stealc
let malicious_ips = dynamic(["144.31.57.70", "160.20.109.75"]);
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(["144.31.57.70", "160.20.109.75"]);
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://185.223.82.171/fd89ba886125940b747e.php", "http://144.31.57.70/c0e070fa9435429c8ea5.php"]);
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 four specific false positive scenarios for the ThreatFox: Stealc IOCs detection rule in an enterprise environment, along with suggested filters or exclusions:

• Endpoint Protection Policy Updates via Microsoft Defender for Endpoint

  • Scenario: The security team pushes a new definition update or policy configuration to workstations using the Microsoft Defender for Endpoint console. This process triggers background tasks that download and execute specific hash values or network connections matching Stealc’s known IOCs (often shared infrastructure or common C2 domains).
  • Filter/Exclusion: Exclude processes originating from MsMpEng.exe (Antimalware Service Executable) or Sense.exe where the parent process is Taskeng.exe (Task Scheduler), specifically targeting the hash values associated with the update package.

• Automated Software Deployment via SCCM (Microsoft Endpoint Configuration Manager)

  • Scenario: A scheduled maintenance window triggers a software deployment job using System Center Configuration Manager (SCCM). The client agent (CcmExec.exe) downloads installation packages from an internal distribution point that utilizes a public CDN or DNS resolution path overlapping with Stealc’s IOCs.
  • Filter/Exclusion: Create a rule exclusion for network connections and file executions where the parent process is CcmExec.exe running under the context of the “System” user, specifically filtering out traffic to known internal distribution point IP ranges or whitelisted CDN domains.

• Third-Party Patch Management Execution (e.g., Ivanti or ManageEngine)

  • Scenario: The IT operations team runs a scheduled patch management job using tools like Ivanti Endpoint Manager or ManageEngine Desktop Central. These agents frequently query external repositories for vulnerability signatures, generating network traffic and file artifacts that match the Stealc IOC set due to shared SSL certificate authorities or common API endpoints.
  • Filter/Exclusion: Exclude events where