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Ransom.MSIL.CRYPCUTE.B

April 10, 2020
 Analysis by: Emilio Marcel Garcia
 ALIASES:

Trojan.MSIL.Filecoder (IKARUS); MSIL/Filecoder.BQ!tr.ransom (FORTINET)

 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:

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.

It encrypts files with specific file extensions. It encrypts files found in specific folders.

  TECHNICAL DETAILS

File Size:

57,344 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

15 Mar 2020

Payload:

Encrypts files, Displays message/message boxes, Terminates processes

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.

Installation

This Ransomware drops the following files:

  • {Malware path}\sendBack.txt - contains RSA key
  • {Malware path}\secret.txt - contains RSA key
  • {Malware path}\secretAES.txt - contains encrypted RSA key
  • {Malware path}\data recive - contains PC name and RSA key

It adds the following processes:

  • "C:\Windows\System32\rundll32.exe" javascript:"\..\mshtml,RunHTMLApplication ";document.write();shell=new%20ActiveXObject("wscript.shell");shell.regwrite("HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce\adr","{Malware path and filename}"

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • cuteRansomware

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
adr = {Malware path and filename}

Process Termination

This Ransomware terminates the following processes if found running in the affected system's memory:

  • taskmgr.exe
  • explorer.exe

Other Details

This Ransomware does the following:

  • It sets the entire screen to the following:

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .png
  • .3dm
  • .3g2
  • .3gp
  • .aaf
  • .accdb
  • .aep
  • .aepx
  • .aet
  • .ai
  • .aif
  • .arw
  • .txt
  • .exe
  • .as
  • .as3
  • .asf
  • .asp
  • .asx
  • .avi
  • .bay
  • .bmp
  • .cdr
  • .cer
  • .class
  • .cpp
  • .cr2
  • .crt
  • .crw
  • .cs
  • .csv
  • .db
  • .dbf
  • .dcr
  • .der
  • .dng
  • .doc
  • .docb
  • .docm
  • .docx
  • .dot
  • .dotm
  • .dotx
  • .dwg
  • .dxf
  • .dxg
  • .efx
  • .eps
  • .erf
  • .fla
  • .flv
  • .idml
  • .iff
  • .indb
  • .indd
  • .indl
  • .indt
  • .inx
  • .jar
  • .java
  • .jpeg
  • .jpg
  • .kdc
  • .m3u
  • .m3u8
  • .m4u
  • .max
  • .mdb
  • .mdf
  • .mef
  • .mid
  • .mov
  • .mp3
  • .mp4
  • .mpa
  • .mpeg
  • .mpg
  • .mrw
  • .msg
  • .nef
  • .nrw
  • .odb
  • .odc
  • .odm
  • .odp
  • .ods
  • .odt
  • .orf
  • .p12
  • .p7b
  • .p7c
  • .pdb
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .php
  • .plb
  • .pmd
  • .pot
  • .potm
  • .potx
  • .ppam
  • .ppj
  • .pps
  • .ppsm
  • .ppsx
  • .ppt
  • .pptm
  • .pptx
  • .prel
  • .prproj
  • .ps
  • .psd
  • .pst
  • .ptx
  • .r3d
  • .ra
  • .raf
  • .rar
  • .raw
  • .rb
  • .rtf
  • .rw2
  • .rwl
  • .sdf
  • .sldm
  • .sldx
  • .sql
  • .sr2
  • .srf
  • .srw
  • .svg
  • .swf
  • .tif
  • .vcf
  • .vob
  • .wav
  • .wb2
  • .wma
  • .wmv
  • .wpd
  • .wps
  • .x3f
  • .xla
  • .xlam
  • .xlk
  • .xll
  • .xlm
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .xml
  • .xqx
  • .zip

It encrypts files found in the following folders:

  • %Desktop% and subfolders

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It renames encrypted files using the following names:

  • {random characters}.RekenSom

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.794.06

FIRST VSAPI PATTERN DATE:

09 Apr 2020

VSAPI OPR PATTERN File:

15.795.00

VSAPI OPR PATTERN Date:

10 Apr 2020

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Troj.Win32.TRX.XXPE50FFF034

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • adr = {Malware path and filename}

Step 6

Search and delete these files

[ 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}\sendBack.txt
  • {Malware path}\secret.txt
  • {Malware path}\secreatAES.txt
  • {Malware path}\data recive

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.MSIL.CRYPCUTE.B. 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 8

Restore encrypted files from backup.


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