URLhaus: malware_download Malicious URLs

Hunt Hypothesis

This hunt targets adversary behavior where endpoints initiate downloads from known malicious URLs identified by URLhaus as delivering malware payloads. Proactively hunting for these specific indicators in Azure Sentinel is critical to intercept early-stage infection vectors before they establish persistence or exfiltrate sensitive data across the cloud environment.

IOC Summary

Threat: malware_download Total URLs: 4 Active URLs: 3

KQL: Url Dns Hunt

// Hunt for DNS resolution of URLhaus malicious domains
// Threat: malware_download
let malicious_domains = dynamic(["i.ibb.co", "42.86.113.243", "pub-b156ef7b8e9141738331d7cd7868c327.r2.dev"]);
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(["i.ibb.co", "42.86.113.243", "pub-b156ef7b8e9141738331d7cd7868c327.r2.dev"]);
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 5 specific false positive scenarios for the URLhaus: malware_download detection rule in an enterprise environment, along with suggested filters or exclusions:

• Endpoint Management Agent Updates via Cloud Repositories

  • Scenario: Managed endpoints (e.g., Microsoft Intune, SCCM, or Jamf) automatically pull definition updates or software patches from cloud storage buckets. These downloads often originate from dynamic IP ranges or generic CDN domains that URLhaus may flag as “malware_download” due to high traffic volume and shared hosting characteristics.
  • Suggested Filter: Exclude traffic originating from known internal management servers or specific vendor FQNs (e.g., *.microsoft.com, *.jamfcloud.com) where the destination port is 443 and the User-Agent header contains the specific agent signature (e.g., Microsoft-Windows-Update-Agent).

• Scheduled Enterprise Antivirus Definition Syncs

  • Scenario: Centralized antivirus consoles (such as CrowdStrike Falcon, SentinelOne, or Symantec Endpoint Protection) trigger scheduled jobs to download large definition packs from vendor update servers. These frequent, high-volume downloads can be misidentified by the rule’s logic which hunts for “malicious” patterns in standard distribution channels.
  • Suggested Filter: Create an exclusion based on the specific destination IP ranges of the antivirus vendor’s update centers combined with a time-based filter (e.g., exclude alerts occurring between 02:00 and 04:00 UTC, coinciding with nightly maintenance windows).

• IT Admin Manual Downloads from Trusted Vendor Portals

  • Scenario: System administrators manually download software installers, drivers, or security patches from official vendor portals (e.g., Cisco Software Download Center, VMware Customer Connect, or Adobe Creative Cloud) to deploy them across the network. These URLs often contain query parameters and session tokens that