The importance of blacklists in cybersecurity

A blacklist is a fundamental tool in cybersecurity that allows blocking digital items that are considered suspicious or malicious in order to protect systems.

What is a cybersecurity blacklist?

One of the most widespread and effective tools in the fight against cyber threats are blacklists. But what exactly are they and how do they work? A cybersecurity blacklist is a database containing IP addresses, domains, emails, applications or any other digital element that has been identified as malicious or suspicious. These items are automatically blocked by security systems to prevent cyber-attacks. Blacklists are used by a variety of security solutions, including firewalls, intrusion detection and prevention systems (IDS/IPS), and anti-virus software.

When a blacklisted item attempts to access a system, the request is automatically rejected.

Public blacklists are maintained by cybersecurity organisations, Internet Service Providers (ISPs), and security software companies. These lists are constantly updated to reflect new threats as they are discovered. In turn, organisations can develop private blacklists to protect their systems from specific threats. If you want to keep up to date with the cybersecurity industry, see our publication→ The 5 cybersecurity trends you need to know about.

Types of blacklists highlighted

There can be as many types of blacklists as there are categories of threats detected. The most prominent are:

IP blacklist

The IP blacklist is a list containing a number of IP addresses identified as potentially dangerous. These IP addresses are often associated with malicious activities, such as sending spam, carrying out DDoS attacks, spreading malware, etc. IP blacklists are used to automatically block traffic from these IP addresses. IP blacklists are used to automatically block traffic from these IP addresses. When an IP address is blacklisted, any attempt to connect from that IP address to a protected system is rejected. IP blacklists are maintained and updated by cybersecurity organisations and Internet service providers. They are constantly updated to reflect new threats as they are discovered or to exclude those that have disappeared. While IP blacklists are a valuable tool in preventing cyber threats, they are not infallible. To avoid blocking, cybercriminals change IP addresses on a recurring basis.

Spam domain blacklist

The spam domain blacklist is a list of domain names that have been identified as sources of spam. These domains may be associated with the distribution of unsolicited emails, phishing, malware and other malicious activities. Spam domain blacklists are used by email security systems and spam filters to automatically block emails from these domains. When a domain is blacklisted, any email sent from that domain to a protected system is marked as spam or rejected. Like all other public blacklists, spam domain blacklists are maintained and updated by cybersecurity organisations, email service providers and security software companies. They are also constantly updated, as cybercriminals frequently change domain names to circumvent them.

How blacklists work

Blacklists are compiled through comprehensive collection and analysis of data on known threats.

The blacklisting process includes:

• Data collection. Data is collected from multiple sources, such as security incident reports, threat intelligence feeds and also internal analysis.
• Data analysis. The collected data is analysed to identify malicious patterns and behaviours. This includes analysis of IP addresses, domains, emails and applications that have been associated with malicious activity such as spam or cyber attacks.
• Creation of the blacklist. Once malicious items are identified, they are added to the blacklist.
• Constant updating. Blacklists should be constantly updated to reflect new threats as they are discovered and to correct detected errors.

Once the blacklist has been compiled, it is used to automatically block access to the organisation’s systems by the digital items on the blacklist.

Main benefits of blacklisting

The use of blacklists for system protection is a solution that provides numerous benefits, among which are:

Easy implementation

Blacklists are relatively simple to implement, making them an attractive option for many organisations. These lists can be easily configured into most security systems, such as firewalls and intrusion detection systems. The ease of implementation allows organisations to quickly improve their security posture without requiring significant resources.

Proactive protection

Blacklists provide proactive security protection by identifying and blocking known threats before they can cause harm. By restricting access to suspicious entities, these lists act as a shield, preventing threat actors from exploiting vulnerabilities. This proactive approach allows organisations to anticipate threats and prevent them from materialising, rather than simply reacting to them once they have occurred.

Complementing security strategies

Blacklists are a valuable complement to other security strategies. They are effective in blocking known threats, but cannot protect against unknown or zero-day threats. Therefore, they are useful as long as they are used in coordination with other techniques, such as anomaly detection and threat intelligence. Together, these strategies provide defence in depth, protecting against a wider range of threats.

Reduction of malicious traffic

Blacklists are very effective in reducing malicious traffic. By blocking IP addresses, domains and emails associated with malicious activity, blacklists significantly decrease the amount of unwanted or harmful traffic. This not only improves security, but also increases network efficiency by reducing the amount of unnecessary traffic.

Limitations of blacklisting

Blacklists are a simple and effective tool to protect systems, however, they have limitations that make it necessary to integrate them into a set of tools.

The main limitations of blacklists are:

False positives

Often, blacklists include erroneous collections or analyses that lead to the blocking of legitimate traffic, an occurrence known as false positives. These false positives harm both the organisation blocking the legitimate traffic and the organisation from which the legitimate traffic originates. To address false positives, many organisations use a combination of blacklisting and whitelisting. Whitelists, in contrast to blacklists, contain items that are considered safe and are allowed. The combination of the two types of lists allows for more granular control and reduces the possibility of false positives.

Need for constant updating

To circumvent blacklist blocking, cybercriminals recurrently change IP addresses, domains or anything that could be blacklisted. Therefore, to remain effective, blacklists require constant updating of their database to reflect new threats as they are discovered, at a significant cost in resources.

 

Implementation of blacklists through Kartos by Enthec

Kartos XTI Watchbots, the Cyber Intelligence platform developed by Enthec, makes it easy for its customers to create private blacklists based on Kartos’ findings and the results of their analyses carried out through our in-house developed artificial intelligence solutions.
In this way, in addition to the protection of general blacklists, our clients add that of private blacklists that respond to the specific context of the organization.
Contact us to learn about the benefits of incorporating our Kartos by Enthec Cyber Intelligence solution into your organization’s Cybersecurity strategy to detect exposed vulnerabilities, open gaps, create blacklists and eliminate false positives.