An ASN — Autonomous System Number — is one of the most useful fields in IP intelligence, yet it's often ignored. It tells you which network an IP belongs to, which is frequently more actionable than the city.
What an ASN is
The internet is a network of networks. Each independently-routed network — an ISP, a cloud provider, a university, a large company — is an Autonomous System with a unique number, like AS15169 (Google) or AS13335 (Cloudflare). BGP, the internet's routing protocol, uses ASNs to decide how traffic flows between these networks.
Why ASNs matter for risk
- Network type: an ASN reveals whether traffic comes from a residential ISP, a mobile carrier, or a datacenter/hosting provider. Datacenter ASNs are a strong bot/proxy signal.
- Reputation: some ASNs are dominated by abuse (bulletproof hosting); scoring by ASN catches whole swaths of bad traffic.
- Stability: ASNs change far less often than precise geolocation, making them reliable for caching and rules.
ASN in practice
A login from a residential ISP's ASN looks very different from one originating in a cloud ASN. The latter is rarely a real human on a phone — it's far more likely a script, scraper, or proxy. detectip.ai exposes ASN and ASN organization, classifies datacenter vs residential, and folds ASN reputation into its risk verdict.
Looking up an ASN
Every detectip.ai verdict includes the IP's ASN and operator alongside geolocation and threat flags. Combine ASN with proxy/VPN detection (see how to detect proxies and VPNs) for a complete picture.
FAQ
Is a datacenter ASN always a bot? Not always — APIs and server-to-server calls are legitimate — but it's rarely an interactive human, so weight it accordingly.
Do ASNs change? Rarely for a given block, which is what makes them reliable.