ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This hunt hypothesis targets adversary behavior characterized by the presence of ten distinct Indicators of Compromise (IOCs) linked to unknown malware, suggesting a potential early-stage infection or lateral movement within the network. The SOC team should proactively execute this hunt in Azure Sentinel to identify and isolate these novel threats before they escalate into widespread incidents, ensuring rapid response against emerging malware variants that may not yet be covered by standard signature-based detections.

IOC Summary

Malware Family: Unknown malware Total IOCs: 10 IOC Types: ip:port, url

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Unknown malware
let malicious_ips = dynamic(["188.166.40.236", "199.247.22.101", "64.177.120.228", "80.240.21.145", "156.38.149.102"]);
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(["188.166.40.236", "199.247.22.101", "64.177.120.228", "80.240.21.145", "156.38.149.102"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - Unknown malware
let malicious_urls = dynamic(["http://41.216.189.236/nz.sh", "https://chorg.xyz/", "https://robinhrood.com/", "https://strastergy.com/", "https://stogagirlssoccer.com/"]);
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 specific false positive scenarios for the ThreatFox: Unknown malware IOCs detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Software Deployment via SCCM/MECM: Large-scale software updates (e.g., Adobe Acrobat or Java patches) distributed through Microsoft Endpoint Configuration Manager often generate new executable hashes and network connections that match the “Unknown” profile before being fully cataloged in the threat intelligence feed.

  • Suggested Filter: Exclude traffic originating from known SCCM distribution points (specific IP ranges) and target processes matching ccmexec.exe or sms_host_ctrl.exe.

• Scheduled Antivirus Definition Updates: The nightly update cycle of enterprise endpoint protection suites, such as CrowdStrike Falcon or Symantec Endpoint Protection, involves downloading new signature databases. These downloads create temporary network flows and file system changes that can be flagged as unknown IOCs by the hunting package.

  • Suggested Filter: Create an exclusion for host groups tagged with “AV-Update-Schedule” during their maintenance window (e.g., 02:00–04:00 UTC) and whitelist the specific vendor update servers (e.g., *.crowdstrike.com, updates.symantec.com).

• IT Admin Script Execution: System administrators frequently run custom PowerShell or Python scripts to perform inventory audits, user provisioning, or log rotation. These scripts often invoke external APIs or download temporary configuration files that lack established reputation scores in the ThreatFox database.

  • Suggested Filter: Whitelist process paths located under C:\Scripts\IT_Operations and exclude network connections initiated by powershell.exe when launched with a -File parameter pointing to internal repository URLs (e.g., gitlab.internal.com).

• Third-Party Cloud Integration Syncs: Automated synchronization jobs between on-premise directories and cloud services like Microsoft