URLhaus: opendir Malicious URLs

Hunt Hypothesis

This hypothesis targets adversaries leveraging the “opendir” malware family to establish initial footholds or execute payloads via compromised web resources, as indicated by the high-severity URLhaus intelligence feed. Proactively hunting for these specific malicious URLs in Azure Sentinel allows the SOC to identify potential lateral movement or data exfiltration attempts before they escalate into broader compromise within the environment.

IOC Summary

Threat: opendir Total URLs: 2 Active URLs: 2

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: opendir
let malicious_domains = dynamic(["sumnitasinvestment.com"]);
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(["sumnitasinvestment.com"]);
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

• Legacy Application Health Checks: Older internal Java or PHP applications may use hardcoded, non-standard health check endpoints (e.g., /api/v1/opendir/status) that are not documented in the main API spec but are actively monitored by Nagios or Zabbix.
  • Filter/Exclusion: Exclude URLs where the path contains /status, /health, or /ping and the HTTP response code is 200 or 302, specifically for internal IP ranges or known legacy application subdomains.
• Developer Localhost Testing: Developers frequently use localhost or 127.0.0.1 with arbitrary path segments for local API testing or mock server configurations. A developer might create a local route named opendir for a specific feature branch test.
  • Filter/Exclusion: Exclude requests where the Host header is localhost, 127.0.0.1, ::1, or matches the regex ^192\.168\.\d+\.\d+$ (private RFC1918 ranges) if the user agent identifies as a development tool (e.g., Postman, Insomnia, curl).
• Scheduled Cron Job Data Fetching: A nightly cron job on a specific application server might fetch configuration or template data from an internal microservice endpoint that coincidentally uses opendir as a resource identifier (e.g., /config/opendir/templates).
  • Filter/Exclusion: Exclude URLs where the User-Agent contains cron, systemd, or ansible, and the request originates from a known application server IP range, specifically if the path ends with .json, .yaml, or .xml.
• Third-Party Integration Webhooks: Some third-party SaaS integrations (e.g., legacy CRM or ERP systems) may use generic or