ThreatFox: BluStealer IOCs

Hunt Hypothesis

This detection rule identifies active threats from the BluStealer infostealer by monitoring for specific indicators of compromise that signal data exfiltration and credential theft within the environment. Proactively hunting for these IOCs in Azure Sentinel is critical to rapidly isolate compromised assets and prevent lateral movement before sensitive information is fully extracted by adversaries.

IOC Summary

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

Type	Value	Threat Type	First Seen	Confidence
sha1_hash	`3de90646a26faadc719b3795c42bd9576e316212`	payload	2026-08-04	95%
md5_hash	`97b43a41d7f2b2cdfb960693da5e97f5`	payload	2026-08-04	95%
sha256_hash	`694483cdead4d874dd33b0a7c11d6c5cbdd1989352c3f7376a71855ad0147dee`	payload	2026-08-04	95%

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - BluStealer
let malicious_hashes = dynamic(["3de90646a26faadc719b3795c42bd9576e316212", "97b43a41d7f2b2cdfb960693da5e97f5", "694483cdead4d874dd33b0a7c11d6c5cbdd1989352c3f7376a71855ad0147dee"]);
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 — BluStealer

False Positive Guidance

Here are 4 specific false positive scenarios and their corresponding exclusion strategies for the ThreatFox: BluStealer IOCs detection rule:

Scenario: Enterprise Antivirus Signature Updates
- Context: The primary endpoint protection solution (e.g., Microsoft Defender for Endpoint or CrowdStrike Falcon) performs a scheduled signature update. The update package often contains hash values or file paths that overlap with known BluStealer IOCs, specifically the bluestealer.exe payload or specific DLL injection patterns used by the vendor’s updater service.
- Filter/Exclusion: Create an exclusion rule to ignore alerts where the Process Name matches MsMpEng.exe (Defender) or csfalcon.exe (CrowdStrike) and the Parent Process is the respective update scheduler service (e.g., UpdateService.exe). Additionally, exclude file paths containing \Program Files\Microsoft Defender Antivirus\.
Scenario: Automated Backup Agent Execution
- Context: Enterprise backup agents (such as Veeam Agent for Windows or Rubrik) run nightly jobs to scan and compress user data. These agents often utilize a generic executable name similar to the stealer’s payload or inject processes into the System context, triggering matches against BluStealer’s network connection IOCs (specifically C2 domains used by backup metadata services).
- Filter/Exclusion: Exclude alerts where the User Account is a dedicated service account (e.g., DOMAIN\BackupSvc) and the Process Command Line contains keywords like “backup”, “snapshot”, or specific agent identifiers. Filter out network connections to known internal backup repository IP ranges rather than external public IPs associated with the threat.
Scenario: Scheduled PowerShell Script for Asset Inventory
- Context: IT Operations teams run a scheduled Task (e.g., via Windows Task Scheduler