ThreatFox: WannaCryptor IOCs

Hunt Hypothesis

This detection rule identifies active indicators of compromise linked to the WannaCryptor ransomware family by monitoring for specific threat intelligence signatures within Azure Sentinel. Proactively hunting for these IOCs is critical because early identification allows the SOC team to isolate affected endpoints before lateral movement and widespread encryption occur, significantly reducing potential business disruption.

IOC Summary

Malware Family: WannaCryptor Total IOCs: 3 IOC Types: sha256_hash, sha1_hash, md5_hash

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - WannaCryptor
let malicious_hashes = dynamic(["4f6839725a41eee6426b1aeed61e7b27e40515d5", "6a4d5ab74aab4d6b8c24edb29d4b6d64", "1738f890d5686b1c17b43166659643dde6ff57fc9ed4143dc9801ae331036273"]);
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 — WannaCryptor

False Positive Guidance

Here are the specific false positive scenarios and corresponding filters for the ThreatFox: WannaCryptor IOCs detection rule:

• Scenario: Legitimate deployment of Microsoft Office 365 updates via Microsoft Endpoint Configuration Manager (SCCM) or Intune. The update agents often generate network connections to known Microsoft cloud endpoints that match the specific IP ranges or domain hashes included in the WannaCryptor IOC set.

  • Suggested Filter: Exclude traffic originating from the MSUpdate service (msupdate.exe) and processes running under the SYSTEM account on managed workstations, specifically when connecting to domains ending in .microsoft.com or .office365.com.

• Scenario: Scheduled backup jobs executed by enterprise data protection tools like Veeam Backup & Replication or Commvault. These agents perform periodic scans and network communications that may trigger the rule if they utilize ports or destination IPs overlapping with the WannaCryptor signature, particularly during off-hours.

  • Suggested Filter: Create an exclusion for process names vrb.exe (Veeam) and commvaultagent.exe, limiting the scope to scheduled execution windows (e.g., 02:00–06:00 local time) where these agents are known to run.

• Scenario: Routine patching activities performed by IT administrators using Windows Update for Business or third-party tools like PDQ Deploy. When pushing critical security patches, the system may initiate connections to Microsoft update servers that coincide with the IOCs defined in the rule.

  • Suggested Filter: Exclude events where the parent process is usoc_dla.exe (Windows Update Delivery Optimization) or pdqdeploy.exe, and restrict detection to non-admin user contexts unless the specific IOC matches a known malicious hash not present in the current patch baseline.

• Scenario: Automated compliance