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FireCrypt Ransomware Packs DDoS Code

Ransomware has become a menace for both consumers and enterprises, and malware authors appear determined to take the threat to the next level by adding new capabilities, such as distributed denial of service (DDoS) functionality.

Ransomware has become a menace for both consumers and enterprises, and malware authors appear determined to take the threat to the next level by adding new capabilities, such as distributed denial of service (DDoS) functionality.

Such is the case with FireCrypt, a recently spotted ransomware family capable not only of encrypting victims’ files, but also of launching a DDoS attack against a URL hardcoded in the source code. The malicious app continuously connects to said URL, but also downloads content from it and saves it to the local machine’s %Temp% folder, ultimately filling it up with junk files.

Discovered by the MalwareHunterTeam, the FireCrypt ransomware is built using a command-line application that also allows the author to create, modify basic settings and save samples in the form of executables. Called BleedGreen, the tool is said to be low end, as it doesn’t enable the modification of settings such as the Bitcoin address for payments, ransom value, contact email address, and more.

However, the builder can disguise the executable under a PDF or DOC icon, and can slightly alter the ransomware’s binary so that the new file would feature a different hash. This technique is usually used to create polymorphic malware that is more difficult to detect by standard anti-virus programs.

The ransomware’s author attempts to trick the potential victim into launching the .exe file, which triggers the infection process. When that happens, FireCrypt immediately kills the Task Manager (taskmgr.exe) process and starts encrypting user’s files using the AES-256 encryption algorithm. The ransomware targets 20 file extensions.

FireCrypt keeps the original file names and extensions, but appends .firecrypt to all encrypted files’ names. As soon as the encryption process has been completed, the malware drops a ransom note on the desktop. The ransom note appears identical to that used by the Deadly for a Good Purpose Ransomware, which was discovered in October 2016, when it was still under development.

According to security researchers, the two ransomware families are closely related, with only a few changes seen in their source code. The Deadly for a Good Purpose Ransomware, for example, wouldn’t encrypt files if the infected computer’s date wasn’t 2017. Both families use the same Bitcoin address, and FireCrypt is believed to be a rebranded version of the original malware.

After dropping the ransom note, FireCrypt proceeds to the DDoS activities, which are currently targeting the official portal of Pakistan’s Telecommunication Authority. The malware connects to and downloads the content to a file in the %Temp% folder. It does that repeatedly, which results in the %Temp% folder filling up fast.

The researchers analyzing the ransomware say that the targeted URL cannot be modified using the ransomware’s builder, and that the so called DDoS attack against the website isn’t efficient. For it to cause real damage, the malware would have to infect thousands of computers at the same time, and would also need for all infected machines to be connected to the Internet simultaneously.

Related: Destructive KillDisk Malware Turns Into Ransomware

Related: Ransomware Campaign Targets HR Departments

Related: Multi-Purpose Ransomware Fuels DDoS Attacks

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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