ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This detection identifies potential initial compromise by monitoring network traffic and endpoint logs for five specific indicators of unknown malware that may represent emerging threats not yet covered by existing signatures. Proactively hunting for these IOCs in Azure Sentinel is critical to enable early containment of novel malicious activity before it escalates into a widespread incident, ensuring the security team stays ahead of evolving adversary tactics.

IOC Summary

Malware Family: Unknown malware Total IOCs: 5 IOC Types: domain, md5_hash, ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Unknown malware
let malicious_ips = dynamic(["178.156.243.177", "176.96.139.22"]);
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(["178.156.243.177", "176.96.139.22"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - Unknown malware
let malicious_domains = dynamic(["securo45z554mw7rgrt7wcgv5eenj2xmxyrsdj3fcjsvindu63s4bsid.onion", "3jpdqv73qlweoytmfinj6ce5hwfblx55poomhfjkqmybdnlktljitbad.onion"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - Unknown malware
let malicious_hashes = dynamic(["2c36a2a36a747ee8e1393724c2558b14"]);
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 — Unknown malware

False Positive Guidance

Here are 5 specific false positive scenarios for the ThreatFox: Unknown malware IOCs detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Automated Security Tool Updates

  • Context: The endpoint protection suite (e.g., CrowdStrike Falcon or Microsoft Defender for Endpoint) automatically downloads and executes new definition updates or heuristic scan engines. These components often generate temporary IOCs that have not yet been ingested into the ThreatFox threat intelligence feed, triggering an “Unknown” alert.
  • Suggested Filter/Exclusion: Create a rule exclusion based on Process Name (e.g., falcon.sys, MsMpEng.exe) and Parent Process ID. Additionally, filter out IOCs where the file hash matches known update signatures from the vendor’s trusted repository list.

• Scenario: Scheduled PowerShell Administrative Scripts

  • Context: IT Operations teams run nightly scheduled tasks using PowerShell to perform inventory checks or configuration drift analysis (e.g., Get-ADUser scripts). These scripts often invoke external APIs or download temporary JSON/XML payloads that generate unique network and file IOCs not present in the current ThreatFox library.
  • Suggested Filter/Exclusion: Exclude alerts where the Command Line contains specific administrative keywords (e.g., Get-, Set-, Invoke-RestMethod) and the process path resides within a trusted admin script directory (e.g., C:\Scripts\Admin\).

• Scenario: Development Environment Artifact Deployment

  • Context: In hybrid environments where DevOps pipelines deploy builds to staging servers, new application binaries or container images are frequently pushed. These newly deployed artifacts contain unique hashes and network connections that appear as “Unknown” until the CI/CD pipeline explicitly updates the threat intelligence feed.
  • Suggested Filter/Exclusion: Apply a