ThreatFox: WannaCryptor IOCs

Hunt Hypothesis

This hunt detects adversary behavior involving specific indicators of compromise (IOCs) linked to the WannaCryptor ransomware family, which often targets unpatched systems through network propagation or phishing vectors. A SOC team should proactively hunt for these IOCs in Azure Sentinel to identify early-stage infections before they escalate into widespread encryption events that disrupt critical business operations.

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	`23a96937277baa16540097119666822d408d8c8afbe3480eefff3074a3ccedfd`	payload	2026-08-01	95%
sha1_hash	`0f3ffec20c80543fd35c6dadbe96d9d2e1065ee0`	payload	2026-08-01	95%
md5_hash	`77d0cf12235bfc6c0d8058a3e4d33f79`	payload	2026-08-01	95%

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - WannaCryptor
let malicious_hashes = dynamic(["23a96937277baa16540097119666822d408d8c8afbe3480eefff3074a3ccedfd", "0f3ffec20c80543fd35c6dadbe96d9d2e1065ee0", "77d0cf12235bfc6c0d8058a3e4d33f79"]);
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 4 specific false positive scenarios for the ThreatFox: WannaCryptor IOCs detection rule, including suggested filters and exclusions tailored for an enterprise environment:

Scenario: Automated Backup Scans by Veeam or Commvault
- Context: Enterprise backup agents (e.g., Veeam Agent, Commvault) often perform deep file system scans that generate high-volume I/O operations. These processes frequently access specific registry keys and network ports associated with the WannaCryptor IOCs while indexing encrypted volumes or verifying backup integrity.
- Filter/Exclusion: Create a rule exclusion based on the Process Name (e.g., VeeamAgent.exe, CommServe.exe) and Parent Process (e.g., vssvc.exe). Additionally, exclude traffic originating from the specific subnet range dedicated to backup infrastructure (e.g., 10.20.50.x/24).
Scenario: Scheduled Antivirus Definition Updates via Windows Update
- Context: The built-in Microsoft Defender or third-party EDR solutions (like CrowdStrike Falcon) trigger scheduled jobs during off-hours to download and install definition updates. These updates often involve network connections to known update servers that match the WannaCryptor IOCs, specifically regarding specific hash values of update packages or registry modifications in HKLM\SOFTWARE\Microsoft.
- Filter/Exclusion: Implement a time-based filter to suppress alerts between 01:00 and 05:00 local time for processes named MsMpEng.exe (Defender) or CcmExec.exe (SCCM). Alternatively, exclude specific IOCs that match the known hash signatures of the latest Microsoft Update CAB files.
Scenario: Legacy Application Migration Scripts Running via Task Scheduler
- Context: IT Operations teams frequently deploy PowerShell scripts or