ThreatFox: WannaCryptor IOCs

Hunt Hypothesis

This hunt detects adversary behavior involving the specific indicators of compromise (IOCs) linked to the WannaCryptor ransomware variant within the Azure Sentinel environment. Proactively hunting for these signals is critical because early identification of WannaCryptor activity enables rapid containment before encryption spreads across the network, minimizing potential data loss and operational downtime.

IOC Summary

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

Type	Value	Threat Type	First Seen	Confidence
sha1_hash	`16b27e574fd32f23eb061fe1c8f699df9d338b54`	payload	2026-07-27	95%
md5_hash	`49272795f5841c4b742e247cfa9d2bc0`	payload	2026-07-27	95%
sha256_hash	`2521192853e4857386d89f555851adfdebde3a939199f939f93068058718e72e`	payload	2026-07-27	95%

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - WannaCryptor
let malicious_hashes = dynamic(["16b27e574fd32f23eb061fe1c8f699df9d338b54", "49272795f5841c4b742e247cfa9d2bc0", "2521192853e4857386d89f555851adfdebde3a939199f939f93068058718e72e"]);
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 the false positive scenarios and corresponding filters for the ThreatFox: WannaCryptor IOCs detection rule:

Scenario 1: Enterprise Backup Agents Scanning Encrypted Archives
- Context: Scheduled backup jobs (e.g., Veeam, Commvault) or antivirus engines (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) scanning large .7z or .zip archives containing legacy documents. These agents often generate specific hashes that match WannaCryptor’s known file signatures when processing compressed data streams.
- Filter/Exclusion: Exclude processes running under the VeeamAgent.exe, CommServe.exe, and MsMpEng.exe service accounts, specifically when the process command line includes parameters related to “archive,” “scan,” or “backup.”
Scenario 2: Patch Management Deployment of Legacy Systems
- Context: Automated patching tools (e.g., SCCM, Ivanti Neurons) deploying updates to older Windows Server instances (Windows Server 2012 R2). During the installation phase, these tools may temporarily write configuration files or logs that match the WannaCryptor IOCs due to shared registry keys or file naming conventions used in legacy patches.
- Filter/Exclusion: Create a rule exclusion for events originating from CcmExec.exe (SCCM) and IvantiAgent.exe where the user context is SYSTEM and the event timestamp falls within the defined maintenance window (e.g., Sunday 02:00 – 06:00).
Scenario 3: Internal Document Management System Processing
- Context: A corporate Document Management System (DMS) like SharePoint or M-Files running scheduled indexing jobs. When the system processes a batch of historical documents, it may generate temporary files with hashes identical to WannaCryptor