URLhaus: opendir Malicious URLs

Hunt Hypothesis

This hypothesis posits that adversaries are leveraging known ‘opendir’ malicious URLs to exfiltrate data or establish command-and-control channels within our Azure environment. Proactive hunting is critical because these specific indicators often bypass standard perimeter defenses, requiring deep inspection of web proxy logs in Sentinel to identify early-stage lateral movement before full compromise occurs.

IOC Summary

Threat: opendir Total URLs: 6 Active URLs: 2

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: opendir
let malicious_domains = dynamic(["41.216.189.236"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses
| order by TimeGenerated desc

KQL: Url Proxy Hunt

// Hunt for web traffic to URLhaus malicious domains
let malicious_domains = dynamic(["41.216.189.236"]);
CommonSecurityLog
| where RequestURL has_any (malicious_domains) or DestinationHostName has_any (malicious_domains)
| project TimeGenerated, SourceIP, RequestURL, DestinationHostName, DeviceAction
| order by TimeGenerated desc

Required Data Sources

References

• URLhaus

False Positive Guidance

Here are specific false positive scenarios for the URLhaus: opendir Malicious URLs detection rule in an enterprise environment, along with recommended filters or exclusions:

• Automated Patch Management Scans

  • Scenario: Enterprise patch management tools like Microsoft System Center Configuration Manager (SCCM) or Ivanti Endpoint Manager frequently scan internal repositories and external vendor sites to validate file integrity. During these scans, the agents may generate HTTP requests containing URL parameters that mimic the opendir signature (e.g., directory traversal strings) while querying software update catalogs.
  • Filter/Exclusion: Create an exclusion rule for traffic originating from known patch management server IP ranges or specific service accounts (e.g., svc_sccm_agent) accessing trusted internal repository domains (e.g., .internal.corp, update.microsoft.com).

• Scheduled Backup and Archive Jobs

  • Scenario: Scheduled backup solutions such as Veeam Backup & Replication or Commvault often perform directory enumeration tasks before initiating data transfers. These jobs may trigger API calls to cloud storage endpoints (like AWS S3 or Azure Blob) using query strings that include opendir logic to verify folder structures, inadvertently matching the malicious URL pattern.
  • Filter/Exclusion: Exclude traffic from backup service accounts and scheduled job windows (e.g., 02:00–04:00 UTC) targeting specific cloud storage buckets or internal file servers where directory listing is a known operational requirement.

• Third-Party Security Scanners and EDR Agents

  • Scenario: Endpoint Detection and Response (EDR) agents like CrowdStrike Falcon, SentinelOne, or network scanners such as Tenable Nessus perform deep content inspection. When scanning for vulnerabilities, these tools often simulate user navigation to test directory permissions, generating URLs with