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What is an ASN Lookup?

An ASN lookup is a query that returns information about the organization controlling a specific block of IP addresses. Every network connected to the internet, such as an internet service provider, a large company, or a university, is assigned a unique Autonomous System Number (ASN) by a regional internet registry. An autonomous system is the network or group of networks that operates under that single identifier. 

When you run an ASN lookup, results typically include the organization name, the ASN itself, the range of IP addresses under that system, the country of registration, and abuse contact details. This data comes from registry records and can also be queried through WHOIS, a protocol used to look up ownership and registration information for internet resources. 

ASN lookups are commonly used by security teams to investigate suspicious traffic, verify whether an IP address belongs to a legitimate service provider, or identify networks associated with malicious activity.