ThreatFox: Unknown malware IOCs

Hunt Hypothesis

This rule detects potential compromise by matching network traffic or endpoint telemetry against seven IOCs linked to an unidentified malware strain, indicating that an adversary may be establishing a foothold or executing malicious payloads. Proactively hunting for these indicators in Azure Sentinel is critical because the lack of a known malware classification necessitates rapid investigation to determine the specific threat actor, impact scope, and necessary containment actions before the unknown variant propagates.

IOC Summary

Malware Family: Unknown malware Total IOCs: 7 IOC Types: sha256_hash, ip:port, url

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Unknown malware
let malicious_ips = dynamic(["209.38.224.48", "106.52.255.211", "187.124.49.109"]);
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(["209.38.224.48", "106.52.255.211", "187.124.49.109"]);
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(["https://cik07-cos.7moor-fs2.com/im/4d2c3f00-7d4c-11e5-af15-41bf63ae4ea0/129fd90846a1e173/9221.txt"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - Unknown malware
let malicious_hashes = dynamic(["13e3e1310dd9e9210ed937a651361be16b554be2d20ce5ae06b1dcf610dda603"]);
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

• Scenario: A DevOps engineer uses curl or wget to download a specific binary or script from a GitHub repository or internal artifact registry (e.g., https://github.com/.../build.sh) for a CI/CD pipeline update, where the SHA256 hash matches one of the 7 IOCs due to a shared dependency or a known benign variant of the file.

  • Filter/Exclusion: Exclude events where the source user account belongs to a devops or ci-cd service group, or filter by process name curl/wget when the destination path is within /opt/ci/ or /var/lib/jenkins/.

• Scenario: An IT administrator performs a manual patching task on a legacy Windows server, downloading a specific .exe installer (e.g., setup.exe for a niche monitoring agent) from an internal file share or a vendor’s download portal, where the file hash coincidentally matches an IOC listed for a rare malware strain.

  • Filter/Exclusion: Exclude events where the source IP is within the internal management subnet (e.g., 10.20.0.0/16) and the process is powershell.exe or cmd.exe executing a download command, or allowlist the specific SHA256 hash for the known vendor installer.

• Scenario: A scheduled task on a Linux application server runs a daily backup script that fetches a configuration file or plugin update from an internal Nexus or Artifactory repository, where the downloaded artifact’s hash matches an IOC due to a shared library component used by both the malware and the legitimate application.

  • Filter/Exclusion: Exclude events where the process is python or bash executing a script from /etc/cron.d/ or /opt/app/scripts/, and the destination