Pierluigi Paganini January 05, 2017

Recently experts from MalwareHunterTeam discovered FireCrypt ransomware, a threat that comes as a malware building kit and includes DDoS code.

Ransomware has become one of the fastest growing threats, new malware implements sophisticated features to avoid detection and rapidly spread among the greatest number of machines.

Recently experts from MalwareHunterTeam discovered a new strain of ransomware dubbed FireCrypt, that includes also a component to launch DDoS attacks.

The experts noticed that FireCrypt continuously connects to s certain URL and downloads content from it and saves it to the local machine’s %Temp% folder. In this way, the malware fills the machine with junk files, the URL is hardcoded in the source code of the malware.

The DDoS component analyzed by the researchers targets the official portal of Pakistan’s Telecommunication Authority (http://www.pta.gov(.)pk/index.php) and downloads the content to a file in the %Temp% folder.

The FireCrypt ransomware is created with a malware builder dubbed BleedGreen and leverages a command-line application that automates the process of putting FireCrypt samples together. BleedGreen allows to rapidly customize the ransomware generating a unique executable with a custom name and a file icon chosen by the creator.

According to the malware researchers the ransomware builder is very trivial.

“Compared to other ransomware builders, this is a very low-end application. Similar builders usually allow crooks to customize a wider set of options, such as the Bitcoin address where to receive payments, the ransom demand value, contact email address, and more.” states a blog post published by Bleepingcomputer.com.

The builder is able to disguise the FireCrypt executable under a PDF or DOC icon, it is also able to make small changes to the binary to make harder the ransomware detection.

The infection process starts when a victim’s launches the executable (EXE file) generated by the builder. The ransomware first kills the Task Manager (taskmgr.exe) process and starts encrypting user’s files with AES-256 encryption.

Files encrypted by FireCrypt are easy to recognize because the malware appends the .firecrypt extension the file name. The ransomware drops a ransom note on the desktop that is identical to that used by the Deadly for a Good Purpose Ransomware and the two malware present many similarities.

“Compared to FireCrypt, the only difference is that the Deadly for a Good Purpose Ransomware also featured a logo at the top of the ransom note, now missing in FireCrypt. But, at a close inspection of Deadly’s source code, MalwareHunterTeam was able to discover that both ransomware versions used the same email and Bitcoin addresses, showing a clear connection between the two, with FireCrypt being a rebranded version of the original Deadly for a Good Purpose Ransomware.” continues the post on Bleepingcomputer.

Let’s close with a reflection on the DDoS component, the target URL cannot be modified by the ransomware builder and the DDoS attack is not effective because it requires to infect a huge number of PCs at the same time that would also be connected to the Internet simultaneously.

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Pierluigi Paganini

(Security Affairs – FireCrypt ransomware, malware)