What is ASN?
How ASN Works
Every device connected to the internet uses an IP address, but behind the scenes, these IP addresses are grouped into networks. ASNs help define the borders of these networks and establish relationships between them for routing purposes. When data is transmitted across the internet, it travels through several networks owned by different organizations. Each of these networks is identified by its ASN. Border Gateway Protocol (BGP), the standard protocol for internet routing, relies on ASN information to direct data packets along the most efficient path. For example, if data is traveling from a user in one country to a server in another, BGP ensures it passes through the appropriate ASes to reach its destination. The ASN system is crucial for this efficient and organized traffic flow.
Types of ASNs
There are two main types of ASNs: Public ASN: Assigned to organizations that need to route traffic to other networks on the internet. These organizations typically operate data centers, internet service providers (ISPs), and content delivery networks (CDNs).
Private ASN: Used for internal routing within an organization that doesn’t interact with external networks at a global scale. These numbers are not advertised publicly.
Why Do You Need an ASN?
If your organization operates a large network or connects directly with multiple external networks, you need an ASN for several reasons: Routing Independence: An ASN allows you to control how your network routes traffic to and from other networks, rather than relying on the policies of your upstream providers. Multi-homing: If your organization connects to more than one ISP for redundancy or improved performance, an ASN is necessary to manage traffic flows between these ISPs using BGP. Improved Security: ASN ownership lets you control your network’s routing, improving your ability to prevent attacks like route hijacking, where malicious actors manipulate traffic flows. Peering Agreements: Having an ASN enables your organization to establish peering agreements with other networks, bypassing ISPs and improving performance by exchanging traffic directly.
How to Check ASN for Spam
Checking an ASN for spam-related activities can help ensure that your ASN (or any other ASN) isn’t flagged for distributing malicious content or spam emails. Many ASN operators, ISPs, and organizations use these checks to maintain their network’s reputation.
Steps to Check ASN for Spam:
Use Blacklist Lookup Tools: There are several online tools that allow you to check if an ASN is associated with spam-related activities or if it is blacklisted on any major spam databases. Some of the most widely used tools are:
Spamhaus Reputation Checker
: Spamhaus is one of the most trusted names for anti-spam services, and their lookup tool can show if an ASN is listed for spam.
You can also check the ASN owner’s domain for IP addresses in Spamhaus SBL to the following link format:
https://check.spamhaus.org/sbl/listings/address of the site/.
For example, if the ASN owner’s website is example.com, the URL to check would be:
https://check.spamhaus.org/sbl/listings/example.com/.
CleanTalk Blacklists
: CleanTalk’s blacklist checker allows you to verify if an ASN or IP address is included in their global anti-spam database, helping to prevent unwanted communications.
Scamalytics
: Scamalytics provides tools for detecting fraudulent activity, including checking if an ASN is associated with scammers or other forms of internet abuse. To use Scamalytics, search for the ASN owner name and Scamalytics on Google, as Scamalytics not directly list the ASN.
Monitoring ASN Activity: Some specialized services provide ongoing monitoring of ASN activity, alerting you if there are suspicious or spammy activities associated with your ASN. ASN Reputation Management: Keep your ASN in good standing by regularly checking logs, ensuring security updates, and avoiding associations with bad actors.
Importance of Checking ASN for Spam
Maintaining Reputation: Being associated with a spam-listed ASN can negatively impact your organization’s reputation and lead to blocked communications.
Email Deliverability: If your ASN is flagged for spam, legitimate emails from your network may be rejected or filtered as spam by recipients. Network Security: Identifying if your ASN is associated with malicious activities can help you detect compromised systems within your network and take corrective actions.
How to Obtain an ASN
ASNs are assigned by Regional Internet Registries (RIRs), such as: ARIN (American Registry for Internet Numbers) for North America RIPE NCC for Europe, the Middle East, and parts of Central Asia APNIC for the Asia-Pacific region LACNIC for Latin America and the Caribbean AFRINIC for Africa To obtain an ASN, organizations must apply through their local RIR and demonstrate they need one, typically because they operate a large network with multiple connections to other networks.
Conclusion
Autonomous System Numbers (ASNs) play a fundamental role in internet routing, helping large networks communicate with one another. Organizations that operate sizable networks or have multi-homing requirements need an ASN to maintain control over their routing policies and ensure efficient, secure traffic management. Moreover, checking an ASN for spam activities is crucial to protect your network’s reputation, security, and email deliverability.