ThreatFox: Stealc IOCs

Hunt Hypothesis

This hunt identifies potential compromise by matching network traffic or host artifacts against known IOCs associated with the Stealc threat actor, a group frequently linked to advanced persistent threats targeting enterprise environments. Proactively hunting for these indicators in Azure Sentinel allows the SOC to detect early-stage intrusion attempts and lateral movement activities before they escalate into significant data exfiltration or ransomware deployment.

IOC Summary

Malware Family: Stealc Total IOCs: 3 IOC Types: url, sha256_hash

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - Stealc
let malicious_urls = dynamic(["http://193.178.158.55/auth.php"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - Stealc
let malicious_hashes = dynamic(["18df0ec2efba162d1774b1bf2233c2c24934d2bda49769e814f24d530a795c38", "124cf79f222ef8b88f4d0e2e474378c5a7ab8a3c513d2434037ef0acfd79c984"]);
DeviceFileEvents
| where SHA256 in (malicious_hashes) or SHA1 in (malicious_hashes) or MD5 in (malicious_hashes)
| project Timestamp, DeviceName, FileName, FolderPath, SHA256, InitiatingProcessFileName
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Stealc

False Positive Guidance

• Scenario: A DevOps team deploys a new microservice using docker-compose that includes a health check script polling an external API endpoint (e.g., https://api.stealc.io/health) which matches one of the Stealc IOCs.
  • Filter/Exclusion: Exclude processes where the parent process is dockerd or containerd-shim, or exclude network connections where the local port is in the ephemeral range and the remote IP belongs to a known internal load balancer subnet.
• Scenario: An IT administrator runs a scheduled PowerShell script (Invoke-StealcCheck.ps1) to verify the status of a legacy backup agent that uses a hardcoded URL matching a Stealc IOC for its heartbeat mechanism.
  • Filter/Exclusion: Exclude events where the process name is powershell.exe and the command line contains specific script paths (e.g., C:\Scripts\Backup\), or exclude based on the specific scheduled task name BackupAgentHeartbeat.
• Scenario: A security testing team performs a red team exercise using a custom tool that mimics Stealc’s C2 behavior to test detection coverage, generating traffic that matches all 3 IOCs.
  • Filter/Exclusion: Exclude events occurring during defined maintenance windows or where the source user account belongs to the RedTeam or SecurityTest security group, or exclude based on a specific tag or metadata field added to the host during testing.
• Scenario: A third-party SaaS application (e.g., a monitoring agent like Datadog or New Relic) updates its configuration to use a new endpoint that coincidentally matches one of the Stealc IOCs due to a shared CDN or API gateway.
  • Filter/Exclusion: Exclude network connections where the local process is a known SaaS agent (e.g., `dat