ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This hypothesis posits that adversaries are deploying previously unseen malware variants characterized by four distinct indicators of compromise to evade signature-based defenses within the Azure environment. Proactive hunting is critical for SOC teams to rapidly identify these novel threats before they establish persistence or exfiltrate sensitive data, ensuring early containment in a cloud-native context.

IOC Summary

Malware Family: Unknown malware Total IOCs: 4 IOC Types: domain

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - Unknown malware
let malicious_domains = dynamic(["kffd3.vexlatech.cc", "gotynotbag.cc", "blakcinwhitexn.cc", "auth-code-check.info"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

Required Data Sources

References

• ThreatFox — Unknown malware

False Positive Guidance

Here are specific false positive scenarios for the ThreatFox: Unknown malware IOCs rule, tailored for an enterprise environment where legitimate “unknown” artifacts often mimic malicious behavior:

• Enterprise Endpoint Protection Scans and Quarantine Actions

  • Scenario: The organization’s primary EDR solution (e.g., CrowdStrike Falcon, SentinelOne, or Microsoft Defender) performs a scheduled deep scan. During this process, the engine may generate temporary IOCs for newly discovered file hashes or network connections that are not yet in the global threat intelligence feed, triggering the “Unknown malware” detection before the local reputation database updates these as benign.
  • Filter/Exclusion: Create an exclusion rule to suppress alerts where the Source IP matches the internal management subnet of the EDR console (e.g., 10.20.50.x) or where the Process Name is explicitly identified as the EDR service executable (e.g., csagent.exe, sssd.exe, or MsMpEng.exe).

• Automated Patch Management and Software Deployment

  • Scenario: Scheduled deployment jobs using tools like Microsoft SCCM, Ivanti, or Ansible push new software updates or hotfixes to endpoints. These deployments often install temporary installer packages, scripts, or configuration files that generate unique network traffic (new DNS queries) and file hashes not previously indexed in the ThreatFox IOC database, appearing as “unknown” anomalies during the deployment window.
  • Filter/Exclusion: Implement a time-based filter to exclude alerts occurring during known maintenance windows (e.g., 02:00 - 04:00 UTC) and add an exclusion for traffic originating from the patch management server’s IP range or specific deployment service accounts (e.g., svc-sccm-deploy).

• **IT Administration