Bogon Filtering

Definition of Bogon Filtering

Bogon filtering refers to the process of filtering out “bogon” IP addresses or packets that carry an unassigned or illegitimate IP address on the internet. These addresses are not assigned to any organization or individual and are typically used for malicious activities, such as spreading malware or launching cyberattacks. Implementing bogon filtering helps better protect networks from these unwanted and potentially harmful packets.


The phonetic pronunciation of “Bogon Filtering” can be represented as: /ˈboʊɡɒn ˈfɪltərɪŋ/Breaking it down:- Bogon: /ˈboʊɡɒn/ (BOE-gon)- Filtering: /ˈfɪltərɪŋ/ (FIL-ter-ing)

Key Takeaways

  1. Bogon filtering helps prevent malicious traffic by blocking IP addresses that are either private, reserved, or unallocated.
  2. Implementing bogon filtering at the border routers of a network can significantly enhance the security and performance of that network.
  3. Regular updates of bogon filtering rules are crucial as IP address allocations change over time.

Importance of Bogon Filtering

Bogon filtering is an important technology term because it refers to the practice of filtering out bogons, which are bogus or illegitimate IP addresses that are either reserved for special use, not yet assigned, or possibly used fraudulently.

By filtering out these invalid IP addresses from incoming network traffic, network administrators can effectively prevent various security threats, including distributed denial-of-service (DDoS) attacks, spoofing, and unauthorized access to sensitive data.

Implementing bogon filtering significantly improves the overall network security and integrity, ensuring a safer and more reliable internet experience for users.


Bogon filtering serves as a preventive measure to combat malicious activity in the realm of computer networks, ensuring the smooth and secure functioning of the internet. It comprises a set of techniques employed by network administrators to block out IP addresses that are either invalid, unregistered, or illegitimate, often referred to as bogons.

These bogons pose a threat to the overall network security as their anonymity enables attackers to launch various internet-based attacks such as DDoS (Distributed Denial-of-Service) or spamming activities. In safeguarding against these potential cyber threats, bogon filtering is implemented at the firewall or router level to shield the connected infrastructure from unauthorized access.

As a key component of best practices in network management, bogon filtering contributes to the improvement of network performance by mitigating unnecessary traffic. Due to the dynamic nature of the IP address allocation procedures, bogon filtering necessitates regular updates of its blacklist, which is maintained by various internet organizations, including IANA (Internet Assigned Numbers Authority) and RIPE (RIPE Network Coordination Centre). By eliminating the illegitimate IP addresses from the network, organizations consequently reduce the potential attack surface, thereby limiting the possibility of havoc caused by cybercriminals.

This proactive approach not only optimizes the network’s resources but also enhances the overall internet experience for its legitimate users.

Examples of Bogon Filtering

Bogon filtering is a security measure to prevent traffic from IP addresses that should not be routable on the public internet. These addresses are either reserved, unallocated, or private. Here are three real-world examples of how bogon filtering is applied:

Internet Service Providers (ISPs): Many ISPs use bogon filtering as part of their security measures to protect their customers’ networks from malicious traffic originating from bogon IP addresses or to prevent their customers’ IP address space from being spoofed. For instance, Comcast, a large ISP in the United States, has implemented bogon filtering within its network infrastructure to enhance security.

Enterprises: Companies with significant network infrastructures often apply bogon filtering at their network perimeters. This helps prevent unauthorized traffic originating from bogon IP addresses from entering their networks and reduces the risk of Distributed Denial of Service (DDoS) attacks. Cisco, a network hardware manufacturer, provides guidelines for implementing bogon filtering on its equipment to help companies secure their networks.

Content Delivery Networks (CDNs): CDNs, such as Cloudflare or Akamai, optimize the delivery of web content and protect websites from malicious traffic. They often use bogon filtering as a security feature to block spoofed IP addresses and bogon IP addresses from accessing their clients’ content. This, as a result, enhances web application security and decreases the risk of cyber-attacks.

Bogon Filtering FAQ

1. What is Bogon Filtering?

Bogon filtering is the practice of blocking internet traffic from IP addresses that belong to reserved, unassigned, or otherwise illegitimate ranges. Bogons are commonly referred to as “bogus IP addresses” and are often used by malicious actors for various cyber attacks. Filtering these addresses helps improve network security and reduce unwanted traffic.

2. Why is Bogon Filtering important?

Bogon filtering is important because it helps protect networks from malicious activities, such as DDoS attacks, spoofing, and scanning. By blocking traffic from bogon IP addresses, network administrators can significantly reduce the risk of attacks, conserve bandwidth, and improve overall network performance.

3. How does Bogon Filtering work?

Bogon filtering works by comparing the source IP addresses of incoming traffic with a list of known bogon IP addresses. If an IP address matches an entry on the list, the network will block or drop the traffic from that address. This filtering can be done on various networking devices, such as routers and firewalls, using access control lists (ACLs), or on intrusion detection systems (IDS) and intrusion prevention systems (IPS).

4. How can I implement Bogon Filtering on my network?

To implement Bogon Filtering on your network, you need to obtain an up-to-date list of bogon IP addresses and configure your network devices to block traffic from these addresses. You can use community-driven or commercial sources to get these lists, such as Team Cymru’s Bogon Reference and the Internet Assigned Numbers Authority (IANA). Once you have the list, add rules to your routers, firewalls, or other security devices to block or deny traffic from the bogon IP addresses.

5. How often should I update my Bogon Filtering list?

It’s essential to update your Bogon Filtering list regularly since new IP address ranges can be assigned or reassigned on the internet. Updating the list at least once a month is a good practice, although some administrators prefer to update their lists more frequently, such as weekly or even daily. Keeping the list fresh ensures that your network is protected from the latest bogon IP addresses.

Related Technology Terms

  • BGP (Border Gateway Protocol)
  • IP Address Spoofing
  • Router Access Control Lists (ACLs)
  • Prefix Filtering
  • Internet Routing Registries (IRRs)

Sources for More Information

  • Wikipedia –
  • Cisco –
  • Cloudflare –
  • Team Cymru –

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