IP to ASN

IPtoASN (iptoasn.com) is a free, programmatically accessible service that maps IP addresses to their Autonomous System Numbers (ASNs) and associated organization information. It provides bulk IP-to-ASN mapping through a simple lookup interface and downloadable dataset files updated daily.

For OSINT investigators and network analysts, ASN-level attribution provides a critical layer of organizational context for IP addresses. While a single IP address may appear isolated, its ASN reveals the organization that controls the entire network block — providing immediate organizational attribution for any IP within that network.

ASN analysis is particularly powerful for infrastructure investigations. When multiple suspicious IPs are found to share the same ASN, they are operated by the same network entity — which may be a single cloud provider, hosting company, or even the same criminal organization operating their own autonomous system. ASN clustering transforms individual IP indicators into organizational attributions.

IPtoASN's downloadable datasets are especially valuable for programmatic investigations. Analysts can download the complete current IP-to-ASN mapping and perform local queries at high volume without API rate limits. This enables bulk enrichment of large IP datasets from SIEM logs, threat intelligence feeds, or network captures.

For threat intelligence research, understanding the ASN distribution of malicious infrastructure reveals hosting preferences of specific threat actors. Nation-state threat actors often use specific hosting providers that offer jurisdiction advantages. Cybercriminal groups establish patterns of preferred hosting ASNs that can be used for attribution correlation.

The service's data also reveals ASN contact information including registered organization name and country, the abuse contact for the network block, and the IP range covered by the ASN. This contact information is directly actionable for abuse reporting and legal process.

IPtoASN's data is derived from BGP routing tables and is updated daily, reflecting the current state of internet routing. Historical ASN assignments may differ from current state.

Document queried IPs, returned ASN numbers, organization names, and query dates for case records. ASN assignments can change when IP blocks are transferred between organizations.