ThreatFox: Formbook IOCs

Hunt Hypothesis

This detection rule identifies Formbook malware activity by monitoring for encrypted command-and-control communications that exfiltrate sensitive credentials, banking details, and system data. A proactive hunt is essential in Azure Sentinel to rapidly isolate compromised endpoints before adversaries can leverage stolen information for lateral movement or financial fraud.

IOC Summary

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

Type	Value	Threat Type	First Seen	Confidence
md5_hash	`930114eafd4d5b3b863c795bb99e9ce5`	payload	2026-08-07	95%
sha256_hash	`f0e29d11e1800cf4ef616458f74cd3cfccd0e39559423344e92574fc78023259`	payload	2026-08-07	95%
sha1_hash	`7ef9a8e90e0f3dc0f51d87eec0fc00716e572e71`	payload	2026-08-07	95%

KQL: Hash Hunt

// Hunt for files matching known malicious hashes
// Source: ThreatFox - Formbook
let malicious_hashes = dynamic(["930114eafd4d5b3b863c795bb99e9ce5", "f0e29d11e1800cf4ef616458f74cd3cfccd0e39559423344e92574fc78023259", "7ef9a8e90e0f3dc0f51d87eec0fc00716e572e71"]);
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 — Formbook

False Positive Guidance

Here are 5 specific false positive scenarios for the ThreatFox: Formbook IOCs detection rule, including suggested filters and exclusions tailored for a legitimate enterprise environment:

Scenario: Scheduled Antivirus Definition Updates via Cloud Sync
- Context: Enterprise endpoints running Microsoft Defender for Endpoint or CrowdStrike Falcon often initiate encrypted outbound connections to vendor update servers (e.g., *.microsoft.com, *.crowdstrike.com) during off-hours. These updates involve large payloads and encrypted TLS handshakes that mimic the exfiltration traffic patterns of Formbook.
- Filter/Exclusion: Create a rule exception excluding traffic where the destination IP belongs to known vendor update ranges (e.g., Microsoft Azure Update IPs) AND the process name is MsMpEng.exe or FalconSensorService. Additionally, add a time-based filter to suppress alerts for these processes between 02:00 and 05:00 local time.
Scenario: Automated Cloud Backup Jobs (e.g., Veeam or Acronis)
- Context: Scheduled backup agents running on file servers or workstations frequently exfiltrate sensitive data to cloud storage providers like AWS S3, Azure Blob Storage, or Google Cloud. The encrypted communication channels used by these backup tools often match the C2 signature of Formbook, triggering false positives during peak backup windows.
- Filter/Exclusion: Exclude alerts where the source process is Veeam.Backup.Service.exe, AcronisCyberProtectService.exe, or similar backup agents. Implement a filter that suppresses detections if the destination domain matches known cloud storage providers (e.g., *.amazonaws.com, *.azurewebsites.net) and the data transfer volume exceeds 50MB within a 10-minute window, which is typical for backups but less