What Is a Blacklist and What Are They Used For?

Few security principles in information technology are as divisive as the blacklist. On the surface, they make a lot of sense. You’ll want to restrict unauthorized programs and utilities in your business network, after all. Their efficacy is debatable, but that’s beside the point.

Today’s guide will be covering the ins and outs of the blacklist. You’ll learn what they do, how they work, and if they are truly vital for modern computing standards. This is very much a cyber security-oriented topic, so you’re in for a treat if you’re new to information assurance.

What Is a Blacklist?

If you think of your stereotypical club scene from a movie, you’ll be familiar with the bouncer. The protagonist might not be on the list, or worse, be on a denied list of some sort. The latter is essentially what a blacklist is. It is a means of denying entry, access, or connectivity to some entity on a computer. There are a few different sorts which are commonly used.

Another way to think of them is parental control software in use by school systems. These are an easy way to prevent commonly known applications from launching on school infrastructure. After all, the students are there to learn, not play Fortnite.

Different Types of Blacklists

As previously mentioned, there are a few different ways to deny access to things. These blacklists can be employed as a means of curtailing inappropriate behavior and resource usage or preventing bad actors from accessing a network as a whole.

Applications

One of the more common uses of a blacklist is to block certain applications from launching. You’ll see these most often in business and educational environments. In business applications, you’re trying to prevent the launching of malicious applications or block access to other means of wasting time that could be better spent on productivity.

For educational use, you’ll often see these employed as a means to keep a student focused. These aren’t 100% foolproof, as will be discussed further on. There are more suitable alternatives for blocking specific applications and the like, which we’ll go into in more depth.

Network Users

Blacklisting network users from accessing certain resources within a connected infrastructure is another common application. This is also not 100% foolproof, but can operate akin to the principle of least privilege. Now, a systems or network administrator might opt just to go with the principle of least privilege. In most cases, a determined bad actor can and will make their way into a network.

That said, these are mostly a stopgap to address security concerns in a network. You’ll see these employed in larger company networks, though their usage isn’t quite as common as it was a decade ago. There have been advances in cyber security that have changed the way administrators and security officers approach the flow and control of network resources.

Domains and IP Addresses

A more common usage of blacklists is blocking specific domains and IP addresses on the edge firewall. This serves as a network-wide way of denying access to social media, known bad domains, and other potentially damaging sites.

As stated with the application blacklists, this isn’t a sure-fire way of handling things. After all, as we’ll discuss later on, the weakest link of any organization is the personnel. While this might help in the interim, blocking certain domains and IP addresses won’t allow security personnel to adapt. You’ll be playing a constant game of cat and mouse.

What Makes a Blacklist?

Defining one of these entities is fairly exhaustive. You’ll have security personnel, IT staff, or any number of computing professionals looking at security repositories for up-to-date information. It becomes a very time-consuming endeavor to apply these sorts of rules across a group as a whole.

Now, you can easily define resources as inaccessible through utilities like Microsoft’s Active Directory or any number of administrative tools in Linux. What it boils down to is finding applications, network resources, websites, and other entities for which you don’t want to provide the means to access.

This can be a wide-sweeping initiative or one where you’re constantly adjusting your needs. However, it does need to be stated this is just one component out of the whole when it comes to the security posture of any organization. As you will hear time and time again, the weakest link in any organization is the people.

You can have an exhaustive and comprehensive blacklist, but it means nothing if you still provide the means for a bad actor to pivot to other portions of a network. Determined individuals can and will bypass blacklists, as you’ve surely seen in your time with school or office work.

Are There Alternatives?

So, with the particulars out of the way, are there alternatives to a blacklist? It shouldn’t be any surprise that there are multiple different ways of approaching a problem in cyber security, and blacklists are easily replaced by a few of these.

Whitelists

The easiest way to think of a whitelist is that it is the opposite of a blacklist. Instead of spending time defining the various rules, applications, and so forth associated with a blacklist, you just define what is allowed. A whitelist gives users a clear and defined set of accessible resources.

Like a blacklist, this does have its shortcomings. If you have any sort of holes in your security implementation, which even top firms do, it can be easy to sidestep this. A whitelist is also going to require exhaustive maintenance, much like its counterpart.

This isn’t a sure-fire method, but it is at least easier to implement as a whole compared to a blacklist. A whitelist could very easily be your first line of defense when it comes to preventing the total scope of damage to your company or organization’s infrastructure as a whole.

Training

If your organization outsources security audits, which they should, you’ll likely have suggestions for continued training. It is 2023, and there really isn’t an excuse for tech illiteracy, especially in sectors where computers are commonplace. Continual workplace training helps to educate your personnel on what to look for when it comes to compromising company resources.

You won’t be able to curtail everything — that’s a pipe dream at best. However, you can cover your bases by making sure your staff is aware and capable of recognizing blatant bad domains, faulty applications, and other common methods of entry for a cyber attack.

Principle of Least Privilege

The principle of least privilege is fairly common with most organizations these days, and for good reason. What this concept entails is only allowing the bare minimum of resources needed to complete a job. You don’t need an accountant to handle things like the command line after all.

Your typical data entry worker likewise won’t need access to important financial data. Rather than giving the keys to the kingdom to your workers, you’re implementing a variety of stop-gaps to prevent access to resources. You can read horror stories online about companies having their entire network compromised because there were zero restrictions in place.

Defense in Depth

So, the final alternative is less a single solution. Instead, it combines multiple actions and controls. Personally speaking, it is foolhardy to trust the whole of your organization’s resources to a single control. A blacklist, whitelist, or whatever else is just one part of the whole. You’re going to want to have a load of different options in place.

That means you’ll be employing firewalls, whitelists, user training, network segmentation, and much more to keep things safe and secure. In most environments, letting a user access unauthorized materials or resources can lead to potential downtime. Now, for schools, that means you have lost access to a great educational aide for your students.

For businesses, the reality is far more dire. Downtime is equivalent to lost money, especially if you’re running any sort of online business.

Are Blacklists Crucial for Modern Computing?

Is a blacklist crucial for modern computing? Not really, but they might serve a useful purpose in an educational environment or for keeping your children from accessing things they shouldn’t. However, when it comes down to it, it is too broad to curtail access to every single damaging and frivolous application or network location. Simply said, there are easier ways to keep your employees or students from accessing things that could compromise the network.

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