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RANSOM_CRYPREN.A

August 16, 2015
 Analysis by: Francis Xavier Antazo
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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 Size:

348,003 bytes

File Type:

EXE

File Compression:

RAR SFX

Memory Resident:

Yes

Initial Samples Received Date:

21 Jul 2015

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:

  • %User Profile%\5.png
  • %User Profile%\gfggg.lnk (points to 5.png)
  • {malware path}\help-decrypt-file.enc

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It drops and executes the following files:

  • %User Profile%\42.exe (detected as RANSOM_CRYPREN.A)

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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

  • My_Program_Already_Present

NOTES:

This Trojan finds files to encrypt in the following drives:

  • C:\
  • D:\
  • E:\
  • F:\
  • G:\
  • H:\
  • T:\

The files it encrypts have their file names appended with .decoder@india.com. It drops the file \help-decrypt-file.enc whenever it finds files to encrypt.

This Trojan encrypts files using the following extensions:

  • .3ds
  • .3fr
  • .3pr
  • .ab4
  • .ac2
  • .accdb
  • .accde
  • .accdr
  • .accdt
  • .adb
  • .ait
  • .apj
  • .arw
  • .asp
  • .awg
  • .backup
  • .backupdb
  • .bak
  • .bdb
  • .bgt
  • .bik
  • .bkp
  • .blend
  • .bpw
  • .cdf
  • .cdr
  • .cdr3
  • .cdr4
  • .cdr5
  • .cdr6
  • .cdrw
  • .cdx
  • .ce1
  • .ce2
  • .cer
  • .cfp
  • .cgm
  • .cib
  • .cls
  • .cmt
  • .cpi
  • .crt
  • .csh
  • .css
  • .csv
  • .dac
  • .db-journal
  • .db3
  • .dbf
  • .dc2
  • .dcr
  • .dcs
  • .ddd
  • .ddoc
  • .ddrw
  • .der
  • .design
  • .dgc
  • .djvu
  • .dng
  • .doc
  • .docm
  • .docx
  • .dot
  • .dotm
  • .dotx
  • .drf
  • .drw
  • .dwg
  • .dxb
  • .erbsql
  • .erf
  • .exf
  • .fdb
  • .ffd
  • .fff
  • .fhd
  • .fpx
  • .fxg
  • .gray
  • .grey
  • .gry
  • .hbk
  • .hpp
  • .ibank
  • .ibz
  • .idb
  • .idx
  • .iiq
  • .incpas
  • .JPEG
  • .JPG
  • .kc2
  • .kdbx
  • .kdc
  • .kpdx
  • .lua
  • .mdb
  • .mdc
  • .mef
  • .mfw
  • .mmw
  • .moneywell
  • .mos
  • .mp3
  • .mpg
  • .mrw
  • .myd
  • .ndd
  • .nef
  • .nop
  • .nrw
  • .ns2
  • .ns3
  • .ns4
  • .nsd
  • .nsf
  • .nsg
  • .nsh
  • .nx1
  • .nx2
  • .nyf
  • .odb
  • .odf
  • .odg
  • .odm
  • .odp
  • .ods
  • .odt
  • .orf
  • .otg
  • .oth
  • .otp
  • .ots
  • .ott
  • .p12
  • .p7b
  • .p7c
  • .pat
  • .pcd
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .php
  • .pot
  • .potm
  • .potx
  • .ppam
  • .pps
  • .ppsm
  • .ppsx
  • .ppt
  • .pptm
  • .pptx
  • .psafe3
  • .psd
  • .ptx
  • .ra2
  • .raf
  • .rar
  • .raw
  • .rdb
  • .rtf
  • .rw2
  • .rwl
  • .rwz
  • .s3db
  • .sas7bdat
  • .sav
  • .sda
  • .sdf
  • .sdo
  • .sldm
  • .sldx
  • .sqlite
  • .sqlite3
  • .sqlitedb
  • .sr2
  • .srf
  • .srw
  • .st4
  • .st5
  • .st6
  • .st7
  • .st8
  • .stc
  • .std
  • .sti
  • .stw
  • .stx
  • .sxc
  • .sxd
  • .sxg
  • .sxi
  • .sxm
  • .sxw
  • .txt
  • .wb2
  • .x3f
  • .xla
  • .xlam
  • .xll
  • .xlm
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .xml
  • .ycbcra
  • .zip

  SOLUTION

Minimum Scan Engine:

9.750

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

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.  
  • %User Profile%\5.png
  • %User Profile%\gfggg.lnk (points to 5.png)
  • {malware path}\help-decrypt-file.enc

Step 3

Scan your computer with your Trend Micro product to delete files detected as RANSOM_CRYPREN.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.

NOTES:

Restore the encrypted files from backup.


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