URLhaus: opendir Malicious URLs

Hunt Hypothesis

This detection rule identifies adversary behavior involving the execution of malicious web resources tagged by URLhaus as “opendir,” which typically indicates unauthorized directory traversal or file enumeration activities within a compromised environment. The SOC team should proactively hunt for these indicators in Azure Sentinel to rapidly isolate potential lateral movement attempts and prevent data exfiltration before they escalate into broader network breaches.

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(["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 Software Update Scans by Endpoint Protection Agents

  • Scenario: Enterprise endpoint protection suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne) frequently perform background integrity checks. These agents often query the opendir repository to fetch the latest malware signature definitions and threat intelligence feeds, triggering connections to known opendir URLs that may be flagged as “malicious” due to their high-volume scanning nature rather than actual compromise.
  • Filter/Exclusion: Exclude traffic originating from specific service accounts (e.g., svc_antivirus, defender-agent) or restrict the rule to exclude destination ports commonly used by update services (e.g., port 443) when the source IP belongs to the “Endpoint Management” subnet.

• Scheduled Vulnerability Assessment Scans

  • Scenario: Internal vulnerability management tools like Tenable Nessus, Qualys, or Rapid7 InsightVM run scheduled jobs to assess web server configurations. During these scans, the tool actively probes external resources, including opendir URLs, to verify SSL certificate validity and response codes. The scanning engine’s behavior mimics a malicious crawler, causing the detection logic to flag the legitimate scan traffic as suspicious activity.
  • Filter/Exclusion: Create an exclusion rule based on the source IP ranges of the vulnerability scanner appliances (e.g., 10.20.50.x) and whitelist specific User-Agent strings associated with these tools (e.g., containing “Tenable,” “QualysGuard,” or “Rapid7”).

• Third-Party Supply Chain Integration Webhooks

  • Scenario: In a Dev