ASN Reputation
ASN reputation assesses whether an Autonomous System Number — the network block announcing an IP range — has a history of hosting abuse, bulletproof providers, or residential versus datacenter traffic. It contextualizes IP verdicts when the same IP moves between benign and hostile ASNs.
ASN reputation moves the question up one level: not “is this address bad?” but “what is the record of the network announcing it?”. An autonomous system that announces ten thousand addresses of which eight hundred are listed for abuse has an operator problem, and every one of its addresses inherits some of that suspicion.
The score is computed from the addresses. Take the prefixes a system announces, count how many of their addresses appear in abuse sources and for what, weigh recent listings over old ones, and compare with systems of similar size. A residential ISP with a few infected subscribers scores very differently from a small host where a quarter of the space is phishing.
It is context, not a verdict. A clean address on a hostile ASN deserves a closer look and a shorter cache lifetime; a listed address on a reputable ASN is probably a compromised customer rather than a willing host. Both readings depend on knowing the ASN’s record.
Example
An address with no listings anywhere sits in a system where 22 % of announced addresses were listed for phishing in the last 90 days. The lookup returns a clean reputation for the address and a hostile one for its ASN, and the analyst treats the silence as “not yet” rather than “clean”.
In isMalicious
Each IP report on isMalicious carries the ASN and its operator, and the ASN page at /threat-intel/asn shows how much of the system’s space is listed and for what, so an address can be read against its network.
Frequently Asked Questions
What is ASN Reputation?
ASN reputation assesses whether an Autonomous System Number — the network block announcing an IP range — has a history of hosting abuse, bulletproof providers, or residential versus datacenter traffic. It contextualizes IP verdicts when the same IP moves between benign and hostile ASNs.
How is ASN Reputation related to ASN (Autonomous System Number)?
ASN Reputation and ASN (Autonomous System Number) are both key concepts in threat intelligence. An Autonomous System Number identifies a collection of IP address ranges under the control of a single organization (an Internet Service Provider, cloud provider, or enterprise). ASNs are used in threat intelligence to identify hosting providers commonly used by attackers.
Related Terms
ASN (Autonomous System Number)
An Autonomous System Number identifies a collection of IP address ranges under the control of a single organization (an Internet Service Provider, cloud provider, or enterprise). ASNs are used in threat intelligence to identify hosting providers commonly used by attackers.
IP Reputation
IP reputation is a score or classification indicating whether an IP address has been associated with malicious activity. Factors include appearance on blocklists, volume of spam sent, history of port scanning, C2 hosting, and abuse reports.
Bulletproof Hosting
Bulletproof hosting providers ignore abuse complaints and allow criminals to host phishing kits, C2 servers, and malware distribution with minimal takedown response. IPs and domains on bulletproof ASNs receive elevated risk scores in threat intelligence platforms.
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