ThreatFox: Vidar IOCs

Hunt Hypothesis

This detection rule identifies adversary behavior consistent with the Vidar infostealer by monitoring for specific Indicators of Compromise (IOCs) such as malicious file hashes and network connections to known command-and-control infrastructure. A SOC team should proactively hunt for these signals in Azure Sentinel because early identification of Vidar activity allows for rapid containment before sensitive credentials and personal data are exfiltrated, mitigating the high risk associated with this prevalent banking trojan.

IOC Summary

Malware Family: Vidar Total IOCs: 3 IOC Types: domain, url

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - Vidar
let malicious_domains = dynamic(["xor.sm188castle.top", "xor.beri303.org"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - Vidar
let malicious_urls = dynamic(["https://sep.beri303.org"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Vidar

False Positive Guidance

Here are 4 specific false positive scenarios for the ThreatFox: Vidar IOCs detection rule, along with targeted filters and exclusions suitable for an enterprise environment:

• Scenario: Scheduled Antivirus/EDR Full Scans

  • Context: During nightly maintenance windows, enterprise EDR solutions (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) perform full system scans. These agents often query internal threat intelligence feeds or download definition updates that share the same hash signatures as known Vidar IOCs, triggering a match on the endpoint’s network traffic or file access logs.
  • Filter/Exclusion: Create an exclusion rule based on Process Name and Time Window. Exclude alerts where ProcessName matches FalconSensor.exe, MsMpEng.exe, or DefenderService.exe occurring between 01:00 and 05:00 local time.

• Scenario: Admin-Initiated Patch Deployment via Configuration Management

  • Context: System administrators use tools like Microsoft SCCM (Configuration Manager) or Ansible Tower to deploy security patches or software updates across the fleet. The deployment agents often download update packages from internal repositories that contain files with hashes identical to Vidar IOCs, causing the detection logic to flag these legitimate downloads as suspicious activity.
  • Filter/Exclusion: Implement a filter based on User Account and Source IP. Exclude events where UserName belongs to the IT-Admins security group or where the source network is within the corporate management subnet (e.g., 10.20.x.x).

• Scenario: Internal Threat Intelligence Platform Synchronization

  • Context: The organization utilizes an internal SIEM or SOAR platform (e.g., Splunk Enterprise Security, IBM QRadar) that periodically syncs with external