ThreatFox: WannaCryptor IOCs

Hunt Hypothesis

This hunt targets WannaCryptor ransomware behavior by identifying initial infection vectors such as phishing attachments or exploit kits followed by lateral movement and anomalous file encryption activities across the environment. Proactively hunting for these indicators in Azure Sentinel is critical to detect early-stage outbreaks before widespread data encryption occurs, enabling rapid containment of the threat within the organization’s cloud infrastructure.

IOC Summary

Malware Family: WannaCryptor Total IOCs: 15 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(["ee2a0f806eea5db5f8ed4e22f52d1b2492e62a6b", "752b88ff4f0f5ea39ac1912c924f2f4d", "1963f2cceff182e761507020f6cd92e54cb5194d", "b0a87d0fcdd49c072364c4378dfc9f8b", "431e527d800caf5391917f79b07bb0650501ded29678edca8627007f629c1bad", "1da954be17c19b2e61d605097f1c7b29", "3b6603d9bd648152700076a8e00a0e23218fd642ce63b5b47891f9db9ec0172b", "48fca9f4433f79d8595fb75fe0940af8177b91b51068c132655472551b91af5a", "e7aae02abc7dc06ef69efeb1e98654dd69efd500", "993e330b2c80db36a50514c5fd50466c", "4caa645feeb04cad5af75a3c5024076e99560678584c84ae07950c9c106d2af0", "55e3f9a3ae32da95511ccff3c3b2fcdde3b87c7a", "53b75c21bfc49c21d1e3998cf2acd14a", "1574e58fb3f049dd10d6923ca6b36bc440160cfdf57407328191ada99d3e1a89", "189661f059be5bc53c2f0a3af5d8bec1540adff3"]);
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 4 specific false positive scenarios for the ThreatFox: WannaCryptor IOCs detection rule, tailored for an enterprise environment:

• Legitimate Patch Deployment via WSUS/SCCM

  • Scenario: The organization’s automated patch management system (e.g., Microsoft Endpoint Configuration Manager or WSUS) pushes a critical security update containing a known WannaCryptor-related vulnerability fix. During the deployment, the system performs registry modifications and file integrity checks that mimic the “unusual encryption activity” and registry changes associated with the ransomware’s initial infection phase.
  • Filter/Exclusion: Create an exclusion rule to suppress alerts for processes originating from trusted patch management executables (e.g., ccmexec.exe, WsusClientHandler.exe) running under the NT AUTHORITY\SYSTEM or specific Service Accounts, specifically when targeting known update KB numbers.

• Scheduled Enterprise Backup Operations

  • Scenario: A nightly scheduled job using enterprise backup software (such as Veeam Backup & Replication, Commvault, or Rubrik) initiates a full backup cycle. This process involves high-volume file I/O and temporary file locking/encryption on the destination storage array, which can trigger alerts for “massive file encryption activity” similar to the ransomware’s payload execution.
  • Filter/Exclusion: Configure time-based exclusions (e.g., 02:00–06:00 local time) and process whitelisting for backup agents (e.g., VeeamAgent.exe, SimEngine.exe). Additionally, exclude alerts where the file extension changes are consistent with standard backup formats (.vbk, .btr, .vmdk) rather than user data extensions.

• Antivirus Engine Scanning and Quarantine

  • Scenario: The endpoint protection suite (e.g., CrowdStrike Falcon