URLhaus: 91-92-40-15 Malicious URLs

Hunt Hypothesis

This hunt targets adversary behavior where compromised hosts initiate outbound connections to a specific cluster of ten known malicious URLs identified by URLhaus under the 91-92-40-15 tag. Proactively hunting for these indicators in Azure Sentinel is critical because early detection of this high-severity activity can prevent data exfiltration and lateral movement before the threat escalates into a broader incident.

IOC Summary

Threat: 91-92-40-15 Total URLs: 10 Active URLs: 10

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: 91-92-40-15
let malicious_domains = dynamic(["91.92.40.15"]);
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(["91.92.40.15"]);
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 3-5 specific false positive scenarios for the URLhaus: 91-92-40-15 Malicious URLs detection rule, including suggested filters and exclusions tailored for a legitimate enterprise environment.

• Scenario 1: Automated Security Scanner Probes

  • Context: Internal vulnerability scanners (e.g., Tenable Nessus, Qualys, or Rapid7 InsightVM) periodically probe external endpoints to validate certificate chains and web server configurations. These tools often generate HTTP requests to known malicious test URLs listed in the 91-92-40-15 feed as part of their baseline “threat intelligence validation” module, even if no actual compromise exists on the host.
  • Suggested Filter/Exclusion: Create an exclusion rule based on Source IP (the scanner’s management server) and Process Name.
    • Filter Logic: Exclude IF Source_IP IN [10.x.x.x, 172.16.x.x] AND Process_Name IN ['Nessus.exe', 'QualysAgent.exe'].

• Scenario 2: Scheduled Endpoint Definition Updates

  • Context: Enterprise EDR agents (such as CrowdStrike Falcon, SentinelOne, or Microsoft Defender for Endpoint) perform scheduled definition updates. During this process, the agent’s background service (Cortex.exe, S1Service.exe) connects to the URLhaus feed server to download threat signatures. The specific IP range 91-92-40-15 is often used as a staging or mirror node for these feeds, triggering the alert during routine maintenance windows (e.g., every Sunday at 02:00 UTC).
  • Suggested Filter/Exclusion: Implement a time-based exclusion combined with specific Process Path verification. *