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Coronavirus Malware Makes Devices Unusable by Overwriting MBR

A newly discovered piece of malware is taking advantage of the current COVID-19 pandemic to render computers unusable by overwriting the MBR (master boot record).

A newly discovered piece of malware is taking advantage of the current COVID-19 pandemic to render computers unusable by overwriting the MBR (master boot record).

Cybercriminals were quick to exploit the coronavirus crisis for their malicious attacks, including phishing, malware infections, and the likes, and it did not take long for state-sponsored threat actors to join the fray.

In addition to banking Trojans targeting enterprise workers and information-stealing malware aimed at multiple industries, which only steal victims’ information, miscreants are also disseminating destructive threats, such as the newly observed wiper.

When executed, the malware drops a series of helper files inside a temporary folder, including a BAT file that identifies itself as “coronovirus Installer,” and which is responsible for most of the setup work.

The file, SonicWall’s security researchers reveal, creates a folder named COVID-19, where it moves the previously dropped helper files. The folder is hidden, which helps the infection go unnoticed.

The so-called installer then disables Windows Task Manager and User Access Control (UAC). It also changes the desktop wallpaper and disables the options that allow the user to add or modify wallpapers. For persistence, the threat adds entries in the registry.

Finally, the malware notifies the victim that the installation has been completed and that the system is going to be rebooted.

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A batch file is then created to ensure that the previously operated registry modifications remain unaltered and to facilitate the launch of an executable file called “mainWindow.exe.”

This file displays a window showing the structure of the COVID-19 virus and two buttons: one named “Remove virus,” which is non-functional, and one named “Help.” When clicked, the Help button alerts the user that the computer was infected.

After the computer is rebooted, a binary is executed to overwrite the MBR, but not before it creates a backup of the original MBR in the first sector. On sector 2 of the disk, a message that reads “Created by Angel Castillo. Your Computer Has Been Trashed” is written.

The message is displayed to the victim by the bootstrap code when the computer starts.

Related: State-Backed Players Join Pandemic Cyber Crime Attacks

Related: Senator Urges Vendors to Secure Networking Devices Amid COVID-19 Outbreak

Related: Corporate Workers Warned of ‘COVID-19 Payment’ Emails Delivering Banking Trojan

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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