Secrets of crypto Trojan revealed

Kaspersky Lab has released important details of the inner workings of the nasty "ransom" Trojan that appeared in early June.

As well as being a new example of the growing scourge of Trojans which encrypt PC data files until a ransom is paid in exchange for a key, the malware signals an the alarming increase in the sophistication of the 660-bit RSA encryption employed.

In fact, only days before, the and .af variants had appeared with 260- and 330-bit encryption, so the step up in complexity was large and unexpected.

Discovered exclusively by Kaspersky, the Trojan family was said to have been circulating across its country of origin, Russia, from the early months of this year.

Kaspersky has now confirmed that spread initially through spam, containing an attachment. If clicked on, infection involved the calling of a Trojan installer, Trojan-Downloader.Win32.Small.crb, which in turn downloaded Gpcode from a website.

Once it had run and encrypted any one or combination of 80 file-types on the PC, Gpcode and the Trojan would delete themselves to confound detection.

Users attempting to open files would be presented with a ransom demand.

"Some files are coded by RSA method. To buy decoder mail: with subject: REPLY," it said. The ransom was to be sent to an account at web portal Yandex, a Russian equivalent to PayPal.

The deeper significance of this variant of Gpcode is its use of public key encryption. In its website explanation, Kaspersky charts the increasing complexity of the encryption used by the malware's authors with each subsequent variant. Every time the length of the private encryption key used to scramble data is increased, more computing power is required to discover the key using brute force.

At some point, this method becomes useless, requiring too much computing resource or time -- potentially tens of years or more -- to succeed.

The key issue is how Kaspersky cracked the encryption on Gpcode, something the company has refused to discuss, presumably for fear of alerting the author to its techniques.

According to Kaspersky, cracking the 330-bit code of Gpcode took a remarkably swift 10 hours, but it admits to being intimidated by the sudden appearance of the 660-bit version.

"Even using a computer with a 2.2 GHz processor it would take 30 years to break such a key. We released detection and decryption routines on the day that was detected. How did we do this? Well, that's a trade secret. And what does the future hold? That's not an easy or a pleasant question," the website notes relate.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

John E. Dunn
Show Comments



Victorinox Werks Professional Executive 17 Laptop Case

Learn more >



Back To Business Guide

Click for more ›

Brand Post

Bitdefender 2018

Roam freely in the digital world. Critically acclaimed performance and security at your fingertips.

Most Popular Reviews

Latest Articles


PCW Evaluation Team

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.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?