ThreatFox: Vidar IOCs

Hunt Hypothesis

This hunt hypothesis targets adversaries utilizing Vidar malware to exfiltrate sensitive data through encrypted command-and-control channels, often initiated by phishing campaigns with malicious URLs or vulnerable document exploitation. Proactively hunting for these indicators in Azure Sentinel is critical due to Vidar’s high severity and its ability to bypass traditional detection mechanisms via encryption, ensuring early identification of potential data breaches before significant information loss occurs.

IOC Summary

Malware Family: Vidar Total IOCs: 4 IOC Types: url, domain

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - Vidar
let malicious_domains = dynamic(["sto.sm188dadu.top", "sto.1131gg.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://sto.sm188dadu.top/", "https://sto.1131gg.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 3-5 specific false positive scenarios for the ThreatFox: Vidar IOCs detection rule, along with suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Legitimate Cloud Backup Agents Communicating with C2-like Endpoints

  • Context: Enterprise backup solutions like Veeam, Rubrik, or Acronis Cyber Protect often utilize encrypted channels to communicate with their management servers. These agents frequently initiate outbound HTTPS connections to specific IP ranges that may overlap with Vidar’s known C2 infrastructure, triggering the rule due to similar traffic patterns (encrypted exfiltration).
  • Filter/Exclusion: Create a whitelist exclusion for the specific process names of these backup agents (e.g., VeeamAgent.exe, rubrik-agent.exe) and their associated service accounts. Additionally, exclude known corporate cloud gateway IP ranges used by these vendors from the rule’s IOC matching logic.

• Scenario: Scheduled Software Update Tasks via Microsoft Endpoint Manager

  • Context: In environments using Microsoft Intune or SCCM, scheduled update tasks often download large payloads from vendor repositories (e.g., Adobe, Zoom, Office 365). These downloads utilize encrypted channels and may hit URLs that share domain characteristics with Vidar’s phishing vectors. The rule might flag the high-volume data transfer during these maintenance windows as suspicious exfiltration.
  • Filter/Exclusion: Implement a time-based filter to suppress alerts for known update windows (e.g., 02:00–04:00 UTC). Alternatively, exclude traffic originating from the specific service account used by the update engine (e.g., NT SERVICE\IntuneAgent) and whitelist the vendor-specific domains (e.g., update.microsoft.com, adobe.io).

• Scenario: Automated Reporting Tools Using External APIs