ThreatFox: XWorm IOCs

Hunt Hypothesis

This hunt targets adversary behavior characterized by the execution of known XWorm indicators of compromise (IOCs) that may signal an active worm infection or lateral movement attempt within the network. Proactively hunting for these specific signatures in Azure Sentinel is critical to rapidly identify and contain potential outbreaks before they propagate across cloud workloads, given the high severity associated with this threat family.

IOC Summary

Malware Family: XWorm Total IOCs: 4 IOC Types: ip:port, md5_hash, sha256_hash, sha1_hash

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - XWorm
let malicious_ips = dynamic(["198.37.105.48"]);
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(["198.37.105.48"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - XWorm
let malicious_hashes = dynamic(["6a26cc31650fd8ca3d62532cd1106899", "7776706d26fb2dfd7cb96910810bb4c3a02b343a228035a0ca4db3ccf8e4d26a", "f04c0953e5169beb168fd9ebcba96ce5d2d38a92"]);
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 — XWorm

False Positive Guidance

Here are four specific false positive scenarios for the ThreatFox: XWorm IOCs detection rule in an enterprise environment, along with suggested filters or exclusions:

• Endpoint Protection Health Checks & Signature Updates

  • Scenario: Enterprise Endpoint Detection and Response (EDR) agents, such as CrowdStrike Falcon, SentinelOne, or Microsoft Defender for Endpoint, frequently initiate background scans that download threat intelligence feeds. These processes often generate network connections to known XWorm indicator IPs or domains used by the vendor’s update servers, mimicking the worm’s propagation behavior.
  • Suggested Filter: Exclude traffic originating from specific EDR service accounts (e.g., svc_crowdstrike, defender-agent) and restrict matching to ports other than standard web traffic (80/443) if the IOCs are primarily HTTP-based, or whitelist the specific vendor update IP ranges in the ThreatFox feed configuration.

• Scheduled Vulnerability Scanning Operations

  • Scenario: Automated vulnerability management tools like Tenable Nessus, Qualys Cloud Agent, or Rapid7 InsightVM run scheduled scans (e.g., nightly at 02:00 UTC) that probe internal assets. These scanners often simulate attack vectors by connecting to external threat intelligence endpoints to validate their own detection logic, triggering matches against the XWorm IOCs during these high-volume scan windows.
  • Suggested Filter: Create a time-based exclusion window (e.g., 01:30–04:30 UTC) for source IPs belonging to the vulnerability scanning subnet or specific scanner service accounts, ensuring that routine health checks do not generate alerts during maintenance hours.

• IT Administration and Patch Deployment Workflows

  • Scenario: During major patch cycles managed by tools like Microsoft SCCM (ConfigMgr), **