ThreatFox: WannaCryptor IOCs

Hunt Hypothesis

This detection rule identifies WannaCryptor ransomware activity by monitoring for specific IOCs associated with phishing-delivered payloads that trigger mass file encryption across infected endpoints. SOC teams should proactively hunt for these indicators in Azure Sentinel to detect early-stage lateral movement and anomalous network traffic, enabling rapid containment before the malware spreads and demands ransom payments.

IOC Summary

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

Type	Value	Threat Type	First Seen	Confidence
sha256_hash	`381ab629fd8f5590643cbc93d9527038da1bc8aeef8ab1c7c2fada6a53be363a`	payload	2026-08-25	95%
sha1_hash	`518758f0de6d8969f456aafc46029bc9cbada419`	payload	2026-08-25	95%
md5_hash	`1d011399cbf80ab0970a15c6c07868d9`	payload	2026-08-25	95%

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - WannaCryptor
let malicious_hashes = dynamic(["381ab629fd8f5590643cbc93d9527038da1bc8aeef8ab1c7c2fada6a53be363a", "518758f0de6d8969f456aafc46029bc9cbada419", "1d011399cbf80ab0970a15c6c07868d9"]);
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

Sentinel Table	Notes
`DeviceFileEvents`	Ensure this data connector is enabled

References

ThreatFox — WannaCryptor

False Positive Guidance

Here are 5 specific false positive scenarios for the ThreatFox: WannaCryptor IOCs detection rule, including targeted filters and exclusions:

Scheduled Enterprise Backup Operations
- Scenario: The organization runs nightly backups using tools like Veeam or Rubrik, which encrypt large volumes of user data (e.g., OneDrive/SharePoint sync folders) between 02:00 and 04:00. This mass file modification and encryption activity mimics the ransomware behavior detected by the rule, triggering alerts on backup agents rather than actual infection.
- Filter/Exclusion: Create an exclusion based on the specific Service Account (e.g., svc-backup-vrm) running the backup process and restrict the alert window to exclude business hours (08:00–18:00). Additionally, filter out file extensions commonly used by backup software (e.g., .vbk, .vib) that are not part of the WannaCryptor target list.
Automated Patch Management and Deployment
- Scenario: The IT team utilizes Microsoft Endpoint Configuration Manager (MECM) or Intune to deploy critical security patches via scheduled jobs. During these deployments, the system may lock and re-encrypt specific configuration files or application binaries as part of the update verification process, generating high-volume file encryption events that resemble ransomware activity.
- Filter/Exclusion: Exclude processes associated with known patching engines (e.g., ccmsetup.exe, msiexec.exe running under the System account) from the detection logic. Implement a filter to ignore alerts where the parent process is identified as a trusted deployment tool and the file changes occur within the designated maintenance window.
Cloud Storage Synchronization and Versioning
- Scenario: Users with **