A New .NET Ransomware Shrug2 Encrypts Files Around 76 Different Extensions

Malware authors find easy to develop malware using the Microsoft .Net framework, some infamous ransomware like SamSam, Lime and now Shrug2 ransomware have been found built with .NET framework.

Shrug ransomware first appeared wild on July 6 embedded with fake software and gaming apps, now it appears it is coming back again with added features.

Quick heal spotted a new version of the ransomware dubbed Shrug2 developed in .NET framework. It attack’s the victim’s machine and demands ransom payments of 70$ in Bitcoins to decrypt the files.

Shrug2 Ransomware Infection

Shrug2 ransomware distributed through Infection Vector such as Phishing Email, Email Attachments, RDP, Embedded Hyperlink, Drive by Infection and Websites & Downloads.

The infection vector of the ransomware is still unknown, once the ransomware infects the victim machine it checks for the active internet connection in the victim machine.

If the victim machine connected to the Internet then it check’s whether the system is already infected with SHRUG2 by checking the registry.

If the system is not infected then it create’s registry entry “[ShrugTwo]” and then it reads the date and time when the ransomware infected the machine and based on that it shows the time left to decrypt the file. It uses AES256 bit key to encrypt the files.

As like any other ransomware it also deletes the system restore points and grants execute a command to all directories and sub-directories.

The ransomware is capable of encrypting 76 file formats.

“txt, .docx, .xls, .doc, .xlsx, .ppt, .pptx, .odt, .jpg, .png, .jpeg, .csv, .mdb, .db, .sln,
.html, .php, .asp, .aspx, .html, .xml, .json, .dat, .cpp, .cs, .c, .js, .java, .mp4, .ogg, .mp3,
.wmv, .avi, .gif, .mpeg, .msi, .rar, .7zip, .z, .apk, .yml, .qml, .py3, .aif, .cda, .mpa, .wpl,
.mid, .pkg, .deb, .arj, .rpm, .gz, .dbf, .yml, .tar, .pl, .rb, .ico, .tif, .asp, .xhtml, .rss,
.jsp, .htm, .o, .zip, .midi, .tiff, .tiff, .midi, .zip, .tar.gz, .pyw, .bmp, .sql, .psd, .7z”

It enumerates the files and creates a to [FilesToHarm] list to encrypt the files and the same list can be used to decrypt the files if the ransom is paid or to delete.

Once the file’s encrypted it add’s “[.]SHRUG2″, and it shows the ransom note and the time left to decrypt the file. The ransomware is also capable of deleting the files if the ransom is not paid.

Quick Heal Security Labs published a blog post with Technical Analysis and Indicators of compromise.

What next: if you’re Infected

• Disconnect the Network.
• Determine the Scope.
• Understand the version or Type of Ransomware.
• Determine the Strains of Ransomware.

Mitigation

• Use Strong Firewall to block the command & control server callbacks.
• Scan all your emails for malicious links, content, and attachment.
• Block the adds and unnecessary web content.
• Enforce access control permission.
• Take regular backups of your data.

Also Read

Ransomware Attack Response and Mitigation Checklist

Ransomware-as-a-Service – Princess Evolution Ransomware Advertised in Underground Forums

Police Department Infected Again by Ransomware Attack that Already Locked 1 Year of Work-Related Files