RANSOM_CRYPCUTE.A

 Analysis by: Rhena Inocencio

 ALIASES:

Win32.Trojan-Ransom.Filecoder.P@gen (GData)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

This Trojan 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 Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

14 Jun 2016

Payload:

Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • {malware path}\sendBack.txt - contains RSA key value
  • {malware path}\secret.txt - contains RSA key value
  • {malware path}\secretAES.txt - contains encrypted key
  • {malware path}\data recive - contains pc name and RSA key value

It adds the following processes:

  • It uses rundll32.exe to run a script that adds its registry entry:
    • "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\uccu","{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 Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
uccu = "{malware path and filename}"

Other System Modifications

This Trojan modifies the following file(s):

  • It encrypts files and names the encrypted files as {random filename}.uccu

It deletes the following files:

  • deletes the original files after producing the encrypted files

Other Details

This Trojan encrypts files with the following extensions:

  • .png
  • .3dm
  • .3g2
  • .3gp
  • .aaf
  • .accdb
  • .aep
  • .aepx
  • .aet
  • .ai
  • .aif
  • .arw
  • .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

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.590.08

FIRST VSAPI PATTERN DATE:

14 Jun 2016

VSAPI OPR PATTERN File:

12.591.00

VSAPI OPR PATTERN Date:

15 Jun 2016

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

Scan your computer with your Trend Micro product and note files detected as RANSOM_CRYPCUTE.A

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
    • uccu = "{malware path and filename}"

Step 6

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}\sendBack.txt
  • {malware path}\secret.txt
  • {malware path}\secretAES.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_CRYPCUTE.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 8

Restore encrypted files from backup.


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