URLhaus: ascii Malicious URLs

Hunt Hypothesis

This hunt identifies potential compromise vectors by correlating user activity with known malicious ASCII-encoded URLs from the URLhaus feed, which are frequently used to host phishing kits or exploit loaders. Proactively hunting for these indicators in Azure Sentinel allows the SOC to detect early-stage web-based intrusions before they progress to credential theft or lateral movement within the tenant.

IOC Summary

Threat: ascii Total URLs: 2 Active URLs: 2

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: ascii
let malicious_domains = dynamic(["get.cativated.win", "get.acttivated.win"]);
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(["get.cativated.win", "get.acttivated.win"]);
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: Old internal web applications or middleware (e.g., legacy Java JSP apps, older versions of Apache Tomcat, or custom .NET services) may contain hardcoded ASCII URLs in configuration files, log headers, or error pages for diagnostic purposes. If these URLs are inadvertently exposed in verbose logs or sent in HTTP headers during routine health checks, they can match the signature.

  • Filter/Exclusion: Exclude traffic where the User-Agent is a known internal monitoring tool (e.g., Zabbix, Nagios, Datadog) or restrict the rule to only trigger on external-facing interfaces, excluding internal service-to-service communication ports (e.g., 8080, 9090).

• API Documentation and Swagger UIs: Development or staging environments often expose API documentation tools like Swagger UI or Postman collections that include example ASCII URLs for testing endpoints. If these environments are accessible via a jump host or internal network, and an analyst or automated script fetches these docs, the ASCII URLs in the JSON/YAML definitions can be captured by network sensors.

  • Filter/Exclusion: Exclude hosts identified as development/staging subdomains (e.g., *.dev.corp, *.staging.corp) or exclude requests where the Content-Type is application/json or application/yaml and the source IP is from the developer VLAN.

• Scheduled Backup and Sync Jobs: Enterprise backup solutions (e.g., Veeam, Commvault) or file sync tools (e.g., Synology Drive, OneDrive for Business) may store metadata or manifest files containing ASCII URLs for remote repository locations. If these manifest files are scanned by endpoint detection or if the backup agent communicates these URLs in log files that are ingested by the SIEM, they can appear as “malicious” URL sightings.

  • *Filter/Exclusion