Don’t run JS email attachments: ​they​ can carry potent ransomware

A new ransomware program called RAA is entirely written in JavaScript

Attackers are infecting computers with a new ransomware program called RAA that's written entirely in JavaScript and locks users' files by using strong encryption.

Most malware programs for Windows are written in compiled programming languages like C or C++ and take the form of portable executable files such as .exe or .dll. Others use command-line scripting such as Windows batch or PowerShell.

It's rare to see client-side malware written in Web-based languages such as JavaScript, which are primarily intended to be interpreted by browsers. Yet the Windows Script Host, a service built into Windows, can natively execute .js and other scripting files out of the box.

Attackers have taken to this technique in recent months, with Microsoft warning about a spike in malicious email attachments containing JavaScript files back in April. Last month, security researchers from ESET warned of a wave of spam that distributes the Locky ransomware through .js attachments.

In both of those cases the JavaScript files were used as malware downloaders -- scripts designed to download and install a traditional malware program. In the case of RAA, however, the whole ransomware is written in JavaScript.

According to experts from tech support forum BleepingComputer.com, RAA relies on CryptoJS, a legitimate JavaScript library, to implement its encryption routine. The implementation appears to be solid, using the AES-256 encryption algorithm.

Once it encrypts a file, RAA adds a .locked extension to its original name. The ransomware targets the following file types: .doc, .xls, .rtf, .pdf, .dbf, .jpg, .dwg, .cdr, .psd, .cd, .mdb, .png, .lcd, .zip, .rar and .csv.

"At this point there is no way to decrypt the files for free," said Lawrence Abrams, the founder of BleepingComputer.com, in a blog post.

The RAA infections reported so far by users display the ransom note in Russian, but even if the threat only targets Russian-speaking users for now, it's only a matter of time until it's distributed more broadly and localized for other languages.

It is very uncommon for people to send legitimate applications written in JavaScript via email, so users should avoid opening this type of file, even if it's enclosed in a .zip archive. There are few reasons for .js files to exist outside websites and Web browsers in the first place.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Father’s Day Gift Guide

Brand Post

PC World Evaluation Team Review - MSI GT75 TITAN

"I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it."

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?