Analysis by: John Anthony Banes
ALIASES:

MSIL/Filecoder.CY!tr (Fortinet); a variant of MSIL/Filecoder.CY trojan (NOD32)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 54,784 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 30 Mar 2017
Payload: Drops files, Encrypts files

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Dropping Routine

This Ransomware drops the following files:

  • {malware path}\master_pri_key.info - private RSA key
  • {malware path}\master_public_key.info - public RSA key

Other Details

This Ransomware encrypts files with the following extensions:

  • .AVI
  • .C
  • .CLASS
  • .CONFIG
  • .CPP
  • .CS
  • .CSC
  • .DBX
  • .DOC
  • .DOCX
  • .EML
  • .GIF
  • .GZ
  • .H
  • .JAVA
  • .JPG
  • .JS
  • .JSON
  • .JSP
  • .MBX
  • .MP3
  • .MP4
  • .MPEG
  • .MSG
  • .NEF
  • .PDF
  • .PHP
  • .PNG
  • .PPT
  • .PPTX
  • .PST
  • .PY
  • .R
  • .RAR
  • .TAR
  • .TXT
  • .VB
  • .VBS
  • .WAB
  • .XAML
  • .XLS
  • .XLSX
  • .ZIP

It does the following:

  • It targets files to encrypt in the following directory:
    D:\TEMP

NOTES:

It displays a console to show the status of encryption or decryption.

For decryption, it checks for “--decrypt” argument.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.310.01
FIRST VSAPI PATTERN DATE: 30 Mar 2017
VSAPI OPR PATTERN File: 13.311.00
VSAPI OPR PATTERN Date: 31 Mar 2017

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.  
  • {malware path}\master_pri_key.info
  • {malware path}\master_public_key.info

Step 4

Scan your computer with your Trend Micro product to delete files detected as Ransom_NXCRYP.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

Step 5

Restore encrypted files from backup.


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