The rise of evil JavaScript – Ransomware and its latest variants

JavaScript is fun.

It’s a simple, logical, straightforward language that has killer programming features, which is why it has become a favorite programming language to build malware (ransomware) among cybercriminals.

You probably know that JavaScript is used to write web-based applications, so obviously you believe it is usually tightly sandboxed in your web browser and can’t really touch the underlying system it runs upon.

..Or is it?

Not really. With NW.js, you can run JavaScript code outside of the Web browser and as a normal desktop application, with more control and interaction with the underlying operating system.

Yes! NW.js is a framework based on Node.js and Chromium that allows you to develop desktop apps for Windows, Linux, and Mac using JavaScript.

However, in Windows, once JS file has been saved to your hard disk, it is run by default outside your browser using a system component called WSH, short for Windows Script Host, without any security warning or requiring administrator access rights.

evil malicious javascript example

Because of this unfortunate behavior in Windows, systems running the Windows OS are being widely targeted by ransomware authors.

That said.

What is Ransomware anyway?

Ransomware is a type of malware designed to block access to a computer system until a sum of money (ransom) is paid.

This is not limited to just individuals; it is widely targeted at businesses. Extortion of money is the prime reason for data security breaches in large companies.

This type of malware initially became quite popular in Russia, where it could be created and attached to small programs with hardly any effort on the part of the hacker. It is a concept that unfortunately continues to persist to this day.

Ransomware is evident across all the Sectors.

Every other industry or sector is affected by ransomware, including healthcare.

According to “Healthcare IT News” and “HIMSS Analytics”, up to 75% of hospitals in the U.S. have been hit by ransomware attacks in the past year, and in some cases, entire hospitals have been taken hostage by ransomware.

How does Ransomware work?

Understanding how ransomware works can prove to be absolutely fascinating.

Ransomware is hardly a new invention and is rather insidious. People have been making ransomware and releasing it for quite some time at this point.

However, there are still a great many people who do not understand how ransomware continues to impact their devices.

Primarily, ransomware arrives at your computer system via email attachments or deceptive pop-ups normally meant for Bait and switch Hacking.

Once it arrives on your system, typically it will act very fast, encrypting all your files, keeping only one copy of the decryption key, and offering to let you buy your data back for a few hundred dollars as a ransom.

For the most part, you can do nothing about decrypting your data unless you actually pay them and get a decryption key.

Having said that most ransomware these days arrives in some sort of email attachment, along with a specially crafted message that encourages you to open the file and look at it, cybercrooks have learned new innovative ways to make the message look legitimate to home users and businesses:


The attached zip file will normally contain a JavaScript file with names such as Invoice.pdf.js, receipt.pdf.js, etc. With the final .js extension being hidden most of the time.

The body of the message tries to convince the user to open the attachment by alerting them to the alleged reference number for their delivery and asking the recipient to show the reference number for successful delivery.

This creates a sense of urgency that may push users to view the attachment.

Opening the .js file in the attachment subjects the user’s system to infection by the ransomware malware, which may download other malware onto the affected system.

Once the file is executed, The ransomware then communicates with its servers. Upon successful connection, the server responds with a public key and a corresponding payment address.

Using asymmetric encryption (a public key to encrypt and a private key for decrypting files), the ransomware begins encrypting all the files that are present on the victim’s computer.

This happens so quickly that the user has very little time to actually realize that his system is being attacked.

Within a few minutes, all the files (including user documents and other important files) are encrypted, and to decrypt them, the user has to pay a fixed ransom amount to the payment address that is displayed on his screen.

ransomware payment script

Upon successful payments, the ransomware then requests its server for a corresponding private key to decrypt the user’s data; without it, decryption is impossible.

Does Antivirus detect them?

No, for the most part. Most ransomware has several layers of defense to thwart antivirus detection.

First of all, they have obscure filenames and unreadable or disguised javascript code that is hard to understand when you look at it statically but nevertheless unravels itself correctly at runtime.

Secondly, it is practically impossible to track ransomware through network traffic monitoring. Since they use Tor and HTTPS connections to make encrypted calls to their servers,

However, there are few antivirus companies like Sophos, Trendmicro, and Bitdefender that have been consistently studying and monitoring ransomware and its variants and have successfully incorporated the corresponding detection mechanism into their products.

Ransomware Attack has become a menace in today’s times.

Over the past 2 years, the ransomware landscape has substantially grown and has been ever-growing since then.

Cybercriminals are extensively using and producing new variants of the ransomware malware due to its easy deployment and potential for huge profits.

Let us look at some of the latest discovered Ransomware variants:

Ransomware variants


Crysis is the smartest ransomware out there and was detected back in February, targeting individuals and enterprises running Windows and Mac OS.

It is smart because it doesn’t just hold a computer’s files hostage; it also has the ability to mine user credentials found in the victim’s system.


CryptXXX has been around for quite some time, but recently it has gained a lot of attention due to its new, updated, stronger encryption technique, which is very hard to crack for any decryption tool.

Apart from regular features, CryptXXX has also been discovered to have Bitcoin-stealing capabilities that steal Bitcoins from your system.


Satana ransomware targets only Windows users.

It is an aggressive ransomware that encrypts the computer’s master boot record (MBR) and prevents it from starting.

The MBR code tells the computer how to start, so when this code gets encrypted, it doesn’t know which disk partitions are where.


BlackShades ransomware, also dubbed SilentShades, targets specifically English and Russian-speaking users, with a ransom pegged at up to 30 USD, payable in Bitcoins only.

Upon execution, it starts encrypting all the user files using 256-bit AES encryption and appends the silent extension to all the encrypted files.


Discovered in June, this ransomware demands affected users email the hacker for ransom amount settlements after encrypting all their files. The victim gets 72 hours or risks losing data.

Interestingly, it was discovered that a victim can bypass the lock screen and run a free decryption tool to regain access to their locked files.


This is the scariest of them all. The name Jigsaw is named after the famous Hollywood thriller SAW.

Victims affected by this malware are presented with a ransom note with the image of the villainous character Billy every hour, with the ransom amount increasing as time passes.


Originally believed to be entirely coded in Plain JavaScript, This ransomware is written using Jscript, a scripting language designed for Windows systems and executed by the Windows Scripting Host Engine via Internet Explorer (IE).

Encrypted files are appended with the .locked extension. The decryption key is made available only when a sum of $250 is paid as ransom amount.


FLocker is primarily targeted at Android Smartphones. It’s lock screen malware that locks your smartphone and demands a ransom. Recently, it has infected smart TVs as well.

It is believed that this ransomware itself has 7,000 different variants.

For someone who is willing to assume the risks and work involved with making ransomware…

You should look for some open-source code-sharing sites, and you should be able to find many Ransomware Toolkits that will allow you to create your own examples.

Ransom32 is new ransomware as a service toolkit which has become quite popular these days.

It is written entirely using JavaScript. Everything is handled through hidden TOR network with Bitcoin as a ransom payment option.

Tox is another good option for creating ransomware, although you will want to note that this kit involves keeping a number of complex steps in mind.

Using Tox is free. All you are going to need to do is register to use the website. You are also going to want to keep in mind that Tox is keenly dependent upon both TOR and Bitcoin.

These are just some of the ransomware toolkits out there these days. As long as you have a decent enough foundation in hacking and creating malware and viruses, you shouldn’t have any trouble using something like Tox or ransom32 to learn how to set about understanding how ransomware works. To be sure, you can certainly make this idea work for you.

Ashwin S

A cybersecurity enthusiast at heart with a passion for all things tech. Yet his creativity extends beyond the world of cybersecurity. With an innate love for design, he's always on the lookout for unique design concepts.