Java Class Files – Here’s How To Protect Them

JAVA Protector: How Can You Protect Your Java Class Files?

In this article, we will discuss how you can protect your files and some real-life case study examples. Furthermore, we will discuss future security trends, how you can prepare for these, and the advantages and disadvantages of the methods discussed.

What Are Java Class Files?

This is arguably the most important question, so we have placed it right at the beginning of the article for this exact purpose. Java class files are defined as stream files. They are produced when the Java compiler compiles a source file.

In addition, the class file contains the unique bytecodes for each method, descriptions used to represent Java objects and static data.

Why Is Java So Important?

In today’s digital environment, data is so important – one leak or mistake can lead to vast amounts of sensitive resources being released or even millions of pounds worth of money being lost or stolen. Therefore, having a secure system in place is imperative.

But again, why use Java? Firstly, Java is by far and away the most popular coding language used worldwide, and for a good reason: it has solid security features, allows code reusability, is dynamic and extensible, and even offers top-of-the-range community support.

We will discuss more of these features later in the article.

Protecting Java Class Files: The Methods

Various methods are available to protect Java Class files, and these will be discussed below in greater detail.

Code Splitting

Sometimes known as code separation, code splitting is defined as splitting the code a web application depends on.

This also includes any third-party dependencies and their code and splitting these into separate bundles that can be located independently.

The reason behind doing this is for an extra layer of security. If a hacker were to try to get access, they would need to understand all the individual relationships and the structure between all the separate parts to make sense of the code.

Not only does it render hacking almost impossible, but it is also a major turn-off for any potential hackers.

This is because it further complicates any reverse engineering attempts, which, of course, makes any hacking attempts hugely time-consuming. And if they were to get through, they would have to reconstruct the source code.

Class Loaders

Class loaders are responsible for loading Java classes dynamically to the JVM (Java Virtual Machine) during run time. Moreover, class loaders are also a part of JRE (Java Runtime Environment).

Because of class loaders, the JVM does not need to know about any underlying files or file systems to run Java programs.

So how do they come in sound from a security point of view?

Because class loaders are customisable, this is essentially what this boils down to. When developers implement a customisable class loader, they can enhance the security of their Java applications.

This typically involves loading classes from encrypted sources or verifying the integrity of loaded classes before execution.

Java Obfuscation

Sometimes known as code obfuscation or bytecode obfuscation, obfuscation in Java is defined as modifying Java bytecode (library or executable) to make it much harder to read and understand while making it wholly functional.

Code obfuscation is usually implemented by renaming variables, classes and methods to non-descriptive names. Developers will also sometimes include bogus code within this to make it even harder for hackers to access it.

Similarly to the code splitting mentioned above, it can be reverse-engineered, although this is massively time-consuming with very little yield for instant results.

This is precisely why obfuscated code is an ideal way to protect class files because it is so frustratingly difficult for hackers to access.

Bytecode Encryption

Bytecode is a type of computer object code. An interpreter converts this code into binary machine code so that a computer’s hardware processor can read it.

However, bytecode encryption involves the class file encryption of the compiled bytecode, with the objective of this complicated procedure being to restrict any unauthorised access.

This is arguably one of the safest methods of class file protection because only a decryption key can execute the encrypted code. This means that no public keys can access the files.

Because it is so complex in the first place, bytecode encryption is easily one of the safest methods of file protection.

Moreover, thanks to its complexity, bytecode encryption is incredibly challenging for any potential cyber attackers or hackers to access the code in the first place, let alone analyse or modify it in any way.

Java Licence Checks

It might not be the first method which comes to your mind when discussing Java class files and their protection, but introducing licence management tools and mechanisms can add an extra layer of security to class files.

This is because only authorised users have access to the files.

To perform this, the developer needs to embed licence checks within the code. In turn, these licence checks require the user to activate the software with valid credentials – it is essentially a code-world version of 2FA or MFA.

Another advantage of these licence checks is that they enable the developers to control software distribution, as well as protect against any unauthorised use, so the developers can add extra layers of security if it is deemed necessary to do so.

Java Class File Protection: Best Practices

While the methods above have been listed as tools and software that can be used when it comes to protecting class files, there is also a range of good practices that can be used when it comes to security.

These are not just necessarily tips and tricks to help you with class file protection but also good practices to implement across all IT and development teams.

Test, Test, Test

How often do you hear the phrase “let’s run another test just to make sure?” in the web development or cybersecurity industry? Our guess is an awful lot!

And it’s for good reason – ensuring that you test the methods regularly means that you can identify any possible gaps or potential issues that might arise before it is too late.

One suggestion is to conduct penetration testing, which can identify any potential vulnerabilities, as well as code reviews which can also do the same.

This means that whichever protection method you opt for will rectify any issues early on. It also shows you that any accidental issues you did not know were associated with the protection method can be avoided at this stage.

Keep On Top of Updates

We’re all guilty of putting off that software update because a notification has popped up while we’re halfway through a task at work.

That, or we’ve been so sure that we already performed an update that this new one cannot be too serious, right?


Staying ahead with your updates is key in any cybersecurity role, especially regarding Java security and protecting class files.

if you have opted for Java code obfuscation as a protection method, updating any obfuscations regularly is a good idea.

Additionally, updating encryption algorithms or licence management processes is equally important so you can stay ahead of any potential threats.

Secure Sensitive Data

When it comes to data being protected, there is good reason for it.

Therefore, ensuring that it is securely protected is incredibly important. The consequences of data leaks or breaches can range from someone’s phone number being released on a public server to a business going under and everything in between.

One good bit of advice is to encrypt data during the transit process and while it is at rest. This reduces the risk of hackers accessing it at these crucial stages and is just a good practice in general.

Furthermore, further security measures such as 2FA (two-factor authentication) or MFA (multi-factor authentication) are also good practices, adding an extra layer to any security between client and server.

Combine Protection Methods

On the subject of adding extra layers of security to the Java class files to protect them, a good idea is to use more than one protection technique.

For example, combining bytecode encryption with code obfuscation can increase the overall security of any Java application and make it twice as hard for cybercriminals to access the data at risk.

The Importance of Education

Within any industry, training your employees is key to identifying the signs of when things are going wrong and spotting problems before they arise – the same applies to any Java platform, too.

Offering courses or bringing external Java or cybersecurity experts into your business can be hugely beneficial, particularly for your development teams.

The effects can be long-lasting and valuable to all business members, whether the external teams are contacted remotely or via an in-person seminar or webinar.

Protection Tools

Below, we will discuss some of the most important protection tools you can use to protect your Java class files.

All the tools mentioned ensure that secure communication is used concerning your files in Java and help keep them safe from potential hackers.

ProGuard Java Optimiser

Perhaps the most well-known Java class file protection tool is the ProGuard Java Optimiser.

Its popularity is largely a result of its versatility – it is a Java class file obfuscator, preverifier, optimiser and shrinker, meaning that whatever you need to do with your Java or JAR files (Java Archive files), you can almost guarantee that the ProGuard Java Optimiser will assist with it.


JavaGuard is another tool which can be used to protect your Java class files. It is a general-purpose bytecode obfuscator, which helps to protect your Java code against forms of reverse engineering or decompilation.

It is also helpful because it fits seamlessly into your regular build and test process, thus making it another attractive option.


If you are searching for a password hashing code, JBCrypt is the most efficient option for you and your business.

It protects your files by hashing passwords through various modifications designed to make password cracking more difficult.

The goal of JBCrypt is to decrease the chance of an attacker compromising a password database, and should they somehow manage to do this, its next aim is to prevent hackers from gaining knowledge of plain text passwords, thanks to its hashing code.


Slightly different from the other methods mentioned above, License4J is a relatively new (established in 2010) Java protection tool that supports floating licences and node-locked ones.

It handles many different security protocols, such as auto-activation, licence generation (hence the name), online key validation, manual activation, deactivation and blacklist check requests. It also stores products, templates and licences in its database.


Another famous Java class file protection option is DashO. This is another obfuscator for Java, which aims to achieve little to no performance loss, even as the complexity of the code increases significantly.

It helps to protect source code from unauthorised decompilation, extraction of code and cyberattacks, making it another attractive option for Java class file protection needs.

Advantages and Disadvantages of Java Class Protection Methods

To provide a balanced overview of the article so far, we will list some advantages and disadvantages of using the various Java class file protection methods.


Reverse Engineering Repression

This is arguably the first advantage that comes to mind when discussing Java class protection methods.

Code obfuscation, in particular, makes this method so important because Java files are susceptible to hackers reverse engineering the original code. As such, obfuscating the code renders it almost impossible for them to hack into the files, let alone steal any data.

Protection of Sensitive Data

As well as intellectual property, Java class files can also help to protect sensitive data, which is particularly important when transferring large files or dealing with large amounts of company or personal data.

Because of their naturally secretive and important nature, class files are often used to deal with sensitive topics, such as documents containing digital signatures or cryptographic algorithms.

Therefore, protecting them is paramount to everyone involved from both sides. By using protection methods such as bytecode obfuscation or encryption, developers can stay in control of their important assets and rest easy knowing they will be protected safely.

Better Software Security

By protecting Java class files, developers have subconsciously added an extra layer of security to their software systems.

Not only is this helpful for the files being protected, but it adds another layer of security to the rest of the software system, helping to protect it from cyber attacks or hackers further.

It is undoubtedly a good practice for developers to get into, as the importance of cybersecurity cannot be underestimated.


Unfortunately, there are also some disadvantages to java class protection files.

Time = Money

As we are all well aware, the phrase time equals money has never been more accurate in business or cybersecurity than it is today.

Unfortunately, Java class protection takes much time to understand, even for the most senior developers.

As a result, it is not an overnight fix or a simple task that anyone can do. Before delving into it, a developer or IT or cybersecurity team must fully understand it.

While the time it takes to understand it can undoubtedly be seen as a disadvantage in the short term, it is important to remember that taking the time to understand it now can save countless hours (and money) in the long run.

Debugging Complexities

While the protection of Java class files needs to be important because of their nature, it is essential to note that it can sometimes be almost too complicated.

The code obfuscation’s incredibly complicated nature – ideal for preventing hackers – can have the reverse effect. It also makes it very hard for the developers to trace, let alone understand, the code, which will lead them to sort out any bugs.

This can sometimes be seen as a double-edged sword.

Security Issues

You may be reading this article and wondering why security issues have only been mentioned now, which is entirely understandable.

The main security issue is that it can lull businesses, companies, organisations and developers into a false sense of security.

This means that with all of the effort, time and money put into protecting Java class files, the company can sometimes be led into thinking that they are safe from all cybersecurity threats.

This is not the case – an equal amount of effort is necessary to go into all other aspects of cybersecurity associated with the business – it cannot rely on Java protection alone.

What Does the Future Hold for Java Protector?

An important question which needs answering concerning the future and trends that we could expect to see in the not-too-distant future.

One such prediction is that there will be a heavier use of Java in more cloud-based environments because of its versatility and because more and more businesses are turning to the cloud for their cybersecurity needs.

It would not be a future trend prediction without mentioning artificial intelligence. Java protection will undoubtedly be used across a range of AI applications, whether that is something like FinOps or DevOps, to protect financial information or simply to assist machine learning about coding and code obfuscation.

Final Thoughts

Throughout this article, it has been widely discussed that the rise of Java is not going away anytime soon.

This also links to the importance of Java protection. With more and more companies and businesses turning to Java when it comes to coding, protecting these files becomes even more critical.

A variety of tools can be used, such as DashO or JavaGuard, all of which have different reasons for being used.

In addition, Java protection has a range of advantages and disadvantages, but it is important to note that the advantages heavily outweigh the disadvantages.

We have also explained how organisations can protect their Java class files through various methods, such as code obfuscation, bytecode encryption, and a range of other tips and tricks that will help keep sensitive data safe, secure, and away from hackers.

If you need more information or would like to contact us, please do not hesitate to contact us.