ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This detection rule identifies potential unknown malware infections by correlating four distinct Indicators of Compromise (IOCs) that may evade signature-based defenses. Proactively hunting for these signals in Azure Sentinel is critical to uncover stealthy threats before they establish persistence or exfiltrate sensitive data, ensuring a rapid response to emerging risks not yet covered by existing threat intelligence feeds.

IOC Summary

Malware Family: Unknown malware Total IOCs: 4 IOC Types: url, domain, ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Unknown malware
let malicious_ips = dynamic(["124.223.53.112", "92.119.158.20"]);
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(["124.223.53.112", "92.119.158.20"]);
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(["blazerpro.pro"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - Unknown malware
let malicious_urls = dynamic(["http://31.56.209.153/nz.sh"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Unknown malware

False Positive Guidance

Here are 5 specific false positive scenarios and corresponding exclusions for the ThreatFox: Unknown malware IOCs rule in an enterprise environment:

• Scenario: Antivirus Engine Updates & Definition Downloads

  • Context: Enterprise endpoints running tools like CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne frequently download new definition packages and engine updates. These downloads often contain new, unsigned hashes that the ThreatFox feed has not yet indexed as “known,” triggering an alert on the first occurrence of these specific IOCs.
  • Suggested Filter/Exclusion: Create a filter to exclude IOCs originating from known vendor update servers (e.g., *.crowdstrike.com, *.microsoft.com) or whitelist file hashes associated with the specific antivirus engine’s update service executable (e.g., C:\Program Files\CrowdStrike\csagent.exe).

• Scenario: Scheduled Patch Management Deployments

  • Context: Automated patch management tools like Microsoft Endpoint Configuration Manager (MECM/SCCM) or Ivanti Neurons deploy new application versions during maintenance windows. The deployment process involves downloading and executing temporary installer packages that may contain IOCs not yet present in the ThreatFox global database, causing alerts on the first rollout of a new patch version across hundreds of machines.
  • Suggested Filter/Exclusion: Exclude alerts where the source process is identified as the patch management agent (e.g., ccmsetup.exe or IvantiAgentService) and the event timestamp falls within the defined maintenance window (e.g., 02:00 – 04:00 UTC on Tuesdays).

• Scenario: Internal DevOps Artifact Distribution

  • Context: Software development teams use internal artifact repositories like JFrog Artifactory, Nexus Repository, or **Azure