URLhaus: opendir Malicious URLs

Hunt Hypothesis

This detection identifies adversary activity involving the exploitation of the “opendir” vulnerability through known malicious URLs that may facilitate remote code execution or data exfiltration. A proactive hunt is essential in Azure Sentinel to rapidly isolate affected endpoints and prevent lateral movement before attackers can establish persistence within the environment.

IOC Summary

Threat: opendir Total URLs: 4 Active URLs: 2

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: opendir
let malicious_domains = dynamic(["31.56.209.153"]);
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(["31.56.209.153"]);
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

False Positive Scenarios for “URLhaus: opendir Malicious URLs”

• Scenario: Automated Software Update Checks by Endpoint Protection Agents

  • Context: Enterprise endpoint security suites like CrowdStrike Falcon, Microsoft Defender for Endpoint (MDE), or SentinelOne frequently perform background connectivity checks against known threat intelligence feeds. These agents often query the opendir feed hosted on URLhaus to validate their local signature databases, triggering legitimate HTTP GET requests that match the rule’s logic.
  • Suggested Filter/Exclusion: Create an exclusion based on the Source Host Group (e.g., “Endpoint Agents”) or filter out traffic where the User-Agent string contains specific vendor identifiers (e.g., CrowdStrike, Microsoft Defender).

• Scenario: Scheduled SIEM Log Ingestion Jobs

  • Context: The organization’s Security Information and Event Management (SIEM) platform, such as Splunk, Elastic Stack, or IBM QRadar, runs a scheduled cron job (e.g., every 15 minutes) to pull the latest threat intelligence data from URLhaus. This ingestion process generates consistent traffic to the opendir endpoint, which is often misidentified as user-initiated browsing activity.
  • Suggested Filter/Exclusion: Exclude alerts where the Source IP belongs to the SIEM management subnet or where the Process Name matches the ingestion service (e.g., splunkd.exe, logstash).

• Scenario: Enterprise Proxy Cache Validation and Health Checks

  • Context: Network security appliances like Zscaler, Palo Alto Networks Cortex XDR, or Fortinet FortiGate perform periodic health checks on their upstream threat intelligence connectors. These proxies often initiate connections to the opendir URL to verify feed availability before routing user traffic