TROJ_RANSOM.CYEA

October 09, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Trojan.Gpcoder.G (Symantec); Troj/Ransom-FM (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

This Trojan encrypts files. When a user clicks on an encrypted file, the following image is displayed:

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.

It uses common file icons to trick a user into thinking that the files are legitimate.

  TECHNICAL DETAILS

File Size:

53,248 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

28 Apr 2012

Payload:

Displays graphics/image

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 copies of itself into the affected system:

  • %User Temp\7S8sm4vtD184St4.exe

It uses common file icons to trick a user into thinking that the files are legitimate.

Other Details

This Trojan encrypts files with the following extensions:

  • *.zip
  • *.rar
  • *.tar
  • *.gzip
  • *.jpg
  • *.jpeg
  • *.psd
  • *.cdr
  • *.dwg
  • *.max
  • *.bmp
  • *.gif
  • *.png
  • *.doc
  • *.docx
  • *.xls
  • *.xlsx
  • *.ppt
  • *.pptx
  • *.txt
  • *.pdf
  • *.djvu
  • *.htm
  • *.html
  • *.mdb
  • *.cer
  • *.p12
  • *.pfx
  • *.kwm
  • *.pwm
  • *.1cd
  • *.mdf
  • *.dbf
  • *.odt
  • *.vob
  • *.ifo
  • *.lnk
  • *.torrent
  • *.mov
  • *.m2v
  • *.3gp
  • *.mpeg
  • *.mpg
  • *.flv
  • *.avi
  • *.mp4
  • *.wmv
  • *.divx
  • *.mkv
  • *.mp3
  • *.wav
  • *.flac
  • *.ape
  • *.wma
  • *.ac3
  • *.asm
  • *.cpp
  • *.pas
  • *.bas
  • *.bbc
  • *.php
  • *.php3
  • *.rbw
  • *.iso
  • *.slddrt
  • *.wmf
  • *.xar
  • *.xmmap
  • *.xml
  • *.mkv
  • *.aim
  • *.kon
  • *.kwd
  • *.lst
  • *.ort
  • *.odt
  • *.odm
  • *.pages
  • *.rzk
  • *.cgi
  • *.vbs
  • *.vbscript
  • *.dxb
  • *.fif
  • *.hpg
  • *.plt
  • *.vsd
  • *.mds
  • *.nrg
  • *.ncd
  • *.img

It renames encrypted files using the following names:

  • {original filename}.QWCiPhErEd

NOTES:

This Trojan creates the following registry entries for all encrypted files to appear as having same icon with that of this Trojan:

HKEY_CLASSES_ROOT\.QWCiPhErEd
@ = "NBTOAEOBJQGIENY"

HKEY_CLASSES_ROOT\NBTOAEOBJQGIENY
@ = "CRYPTED!"

HKEY_CLASSES_ROOT\NBTOAEOBJQGIENY\DefaultIcon
@ = "C:\DOCUME~1\WINXP~1.KAR\LOCALS~1\Temp\7S8sm4vtD184St4.exe,0"

It creates the following registry entry to enable this malware to run every time a user opens an encrypted file:

HKEY_CLASSES_ROOT\NBTOAEOBJQGIENY\shell\open\command
@ = "%User Temp\7S8sm4vtD184St4.exe"

Once a user clicks an encrypted file, the following image is displayed:

It then drops the file HOW TO DECRYPT FILES.txt in all folders and subfolders. The contents of the said file is the same as the text that appears in the image above.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and terminate files detected as TROJ_RANSOM.CYEA

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

 
  • In HKEY_CLASSES_ROOT
    • NBTOAEOBJQGIENY
  • In HKEY_CLASSES_ROOT
    • .QWCiPhErEd

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_RANSOM.CYEA. 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 this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.


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