ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This hypothesis posits that adversaries are actively deploying unknown malware variants within the Azure environment, evidenced by the presence of eight specific indicators of compromise (IOCs) flagged by ThreatFox. Proactive hunting for these IOCs is critical to identify early-stage infections before they escalate into widespread incidents, ensuring rapid containment and minimizing potential data exfiltration risks.

IOC Summary

Malware Family: Unknown malware Total IOCs: 8 IOC Types: ip:port, domain, url

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Unknown malware
let malicious_ips = dynamic(["209.127.36.71", "38.180.204.13"]);
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(["209.127.36.71", "38.180.204.13"]);
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(["authorization-cdn-press-enter.info", "saylror-strategy.com", "claudeai-mythos.com"]);
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://209.127.36.71:2938/juche/bongyeo/chongsang", "http://209.127.36.71:2938/juche/bongyeo/background/background.png", "http://38.180.204.13/ryoheina/mort.php"]);
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 4 specific false positive scenarios for the ThreatFox: Unknown malware IOCs detection rule in an enterprise environment, along with suggested filters or exclusions:

• Endpoint Security Agent Self-Updates and Signature Refreshes

  • Scenario: Enterprise Endpoint Detection and Response (EDR) solutions like CrowdStrike Falcon, SentinelOne, or Microsoft Defender for Endpoint frequently download new definition packs, heuristic engines, or agent binaries. These updates often contain newly signed executables or scripts that have not yet been indexed in the ThreatFox global reputation database, triggering “Unknown” status alerts on the host’s update service account (e.g., SYSTEM or LocalService).
  • Filter/Exclusion: Create a rule exception to exclude IOCs originating from known vendor namespaces (e.g., *.crowdstrike.com, *.sentinelone.net) and restrict alerting to non-system accounts. Additionally, whitelist the specific file paths where these agents store temporary update files (e.g., C:\ProgramData\CrowdStrike\...).

• Scheduled Patch Management Deployments via SCCM or Intune

  • Scenario: During nightly maintenance windows, tools like Microsoft Endpoint Configuration Manager (MECM/SCCM) or Microsoft Intune deploy application patches and custom scripts. These deployments often utilize temporary executable wrappers or PowerShell scripts generated dynamically for the specific tenant environment. Since these artifacts are unique to the organization’s internal repository, they appear as “Unknown” IOCs until manually ingested into ThreatFox.
  • Filter/Exclusion: Implement a time-based filter to suppress alerts during defined maintenance windows (e.g., Sunday 02:00–06:00 UTC). Furthermore, exclude IOCs associated with the CCMExec or IntuneManagementExtension service accounts and file paths located within the standard deployment