Comprehensive Insights into IP Blocklists: An In-Depth Guide

11 December 2023 | by Xavier Bellekens


In today’s digital era, where cyber threats lurk at every corner, the importance of robust security measures cannot be overstated. Among these protective strategies, IP blocklists, also known as IP blacklists, stand out as a key defense mechanism. These lists play a pivotal role in safeguarding against a variety of online threats, from minor annoyances to severe security breaches. This article aims to provide a thorough understanding of IP blocklists, delving deeper into their functionality, significance, and implementation across different digital platforms and networks. By exploring the various aspects of IP blocklists, we offer insights into how they operate as a first line of defense in the complex world of cybersecurity.

What is an IP address Block list?

An IP blocklist, widely known as an IP blacklist, is essentially a database of IP addresses identified as sources of undesirable or harmful internet activities. These blocklists are comprehensive, covering not only individual IPs but also ranges of addresses linked to malicious behaviour.

Such lists are integral in shielding servers, mail servers, internet service providers, and other networked systems from a barrage of digital threats. The use of IP blacklists is a proactive approach to filter and block harmful traffic, thereby safeguarding the integrity and security of digital systems. Understanding the role and scope of these blocklists is fundamental for anyone involved in network management, digital security, or even individual users who wish to protect their online presence.

Understanding Malicious IP Addresses

Malicious IP addresses are those that have been implicated in harmful or unauthorized online activities, such as the distribution of malware, orchestrating cyber attacks, or engaging in online fraud and carrying out cyberattacks. These IP addresses become flagged in various IP blacklists due to their history of malicious behaviour, which can include a range of activities from minor policy violations to severe security threats. Identifying and managing these malicious IPs is a complex process that involves constant monitoring, analysis, and updates to ensure that new threats are promptly addressed. The categorization of an IP as malicious is a critical step in maintaining online safety and is typically handled by specialized cybersecurity agencies and software.

Causes for IP Address Blacklisting

IP addresses can be blacklisted for a myriad of reasons. Most commonly, these include activities like distributing spam emails, hosting malicious content such as viruses or phishing sites, participating in DDoS attacks, being part of a botnet, or simply carrying out scanning for known vulnerabilities.

These activities often lead to an IP being flagged as a threat. This can happen due to a variety of reasons such as shared hosting environments, misconfigurations, or unauthorized use of an IP address. The consequences of being wrongly blacklisted can be significant, affecting communication, access to services, and tarnishing the reputation of the associated domain or network.

Another cause for a valid IP address being blacklisted could be that your organisation has been compromised and you are currently enrolled in a known botnet, scanning the internet service providers for new targets.

Finding and Identifying Blocked IP Addresses

For administrators, webmasters, and IT professionals, identifying whether an IP address is on a blacklist is a critical task. This is typically accomplished using specialized blacklist checker tools such as Lupovis Prowl.

Lupovis will then determine if your specific IP address is listed in it’s global blocklist. This verification process is essential for maintaining the health and reputation of a network or domain. If an IP is mistakenly blacklisted, it can lead to significant communication barriers, email delivery issues, and a loss of trust among clients or users. Consequently, regular checks and prompt action to resolve any blacklisting issues are integral to effective digital management.

Reputation Intelligence: Beyond Traditional Blacklisting

Reputation Intelligence represents an advanced evolution in the realm of IP blacklisting. This approach melds the traditional methods of blacklisting with cutting-edge analytics and predictive modelling. By evaluating an IP address’s history of behaviour and current activity patterns, Reputation Intelligence tools can offer a nuanced view of an IP’s trustworthiness. This level of insight is crucial in preemptively identifying potential risks and threats, thereby providing a more proactive and effective means of protecting digital assets.

Dynamic IP Blocklists for Enhanced Infrastructure Security

Dynamic IP blocklists are a game-changer in the fight against cyber threats. These blocklists are updated in real-time, reflecting the latest intelligence on IP addresses associated with malicious activities. By integrating dynamic blocklists into network security systems, organisations can ensure a more responsive and effective defence against emerging threats. This real-time updating capability is essential in an online landscape where threats evolve rapidly, ensuring that

Where to find an IP address block list?

Lupovis ($79,99/month)

At Lupovis we monitor the state of the internet minute by minute with sensors deployed around the world. The sensors record every interaction, and use data analysis and machine learning to categorize the type of interaction through behavioural analysis. i.e. Mass Scanner, Searching for a Zero-day, known vulnerability, WordPress Exploitation and much much more.

We then analyse the set of interactions from a single adversary and we categorize adversaries, such as script kiddie, ransomware groups, APTs.

Based on all of the suspicious activity we collate, we then create appropriate IP blacklists for to use. The dynamic blocklist is updated every 60seconds ensuring that you are always protected from the latest threats.

Spamhaus Project ($200/month)

One of the most widely recognized free IP blocklists is the Spamhaus Project, known for its extensive database of spam-related IPs.


Another notable option is the OpenBL project, which focuses on listing IPs engaged in brute force attacks and other malicious activities.

Project Honey Pot

Additionally, Project Honey Pot is a unique service that identifies spam and abuse-related IPs by gathering data from its network of websites.

While these blocklists are invaluable resources, it’s important to note that their effectiveness can be limited. Being free, they often face challenges in staying up-to-date with the rapidly evolving landscape of cyber threats. This can lead to instances where new malicious IPs are not promptly added, or, conversely, where IPs are no longer a threat but remain listed. Consequently, while these free services provide a good starting point for IP blocking, they should ideally be supplemented with other security measures for comprehensive protection.

Implementing IP address Block list: Practical Examples with Fortinet Firewalls and WordPress Websites

Utilizing IP blocklists effectively is key to enhancing the security of your digital infrastructure, whether it be a network protected by a Fortinet firewall or a WordPress website. For instance, in the context of a Fortinet firewall, administrators can leverage the firewall’s robust security features to implement blocklists. This is done by accessing the firewall’s management interface, navigating to the security policies section, and then creating or modifying a policy to include the desired IP blocklist.

This policy then actively blocks traffic from the listed IPs, thereby safeguarding the network from potential threats.

On the other hand, for a WordPress website, the process involves using plugins like Lupovis Prowl allows for easy integration of IP blocklists. This plugin provides a user-friendly interface where website administrators can input or upload lists of malicious IP addresses. Once added, the website automatically denies access to these IPs and protect the site, domain and the accounts from cyberattacks, thus preventing potential breaches or unauthorized access.

11 December 2023 | by Xavier Bellekens

Speak to an Expert

Whether you have a specific security issue or are looking for more information on our Deception as a Service platform, simply request a call back with one of our security experts, at a time that suits you.