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TROJ_CRYPCTB.JK

March 07, 2015
 Analysis by: Cris Nowell Pantanilla
 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:

Spammed via email


This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

55,296 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Feb 2015

Payload:

Connects to URLs/IPs, Downloads files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

This Trojan drops the following file(s)/component(s):

  • %User Temp%\{original file name}.rtf

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • {BLOCKED}tionsinc.com/data-test/hello.tar.gz
  • ppc.{BLOCKED}a.pl/cache/hello.tar.gz
  • {BLOCKED}l.cat/IESABP/hello.tar.gz
  • {BLOCKED}uta.com/templates/hello.tar.gz

It saves the files it downloads using the following names:

  • %User Temp%\{random number}.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • windowsupdate.microsoft.com

It opens the following files:

  • %User Temp%\{original file name}.rtf

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

NOTES:

This Trojan drops an archive file %User Temp%\{random}.{extension}, which contains the non-malicious RTF document. The {extension} can be any of the following:

  • 3gp
  • avi
  • bin
  • bmp
  • cda
  • chm
  • dat
  • dll
  • doc
  • exe
  • fb2
  • flv
  • gif
  • hlp
  • iso
  • jpg
  • mdb
  • mdf
  • mds
  • mdv
  • mp3
  • mpg
  • nrg
  • ogg
  • pdf
  • png
  • ppt
  • rtf
  • swf
  • ttf
  • txt
  • vob
  • wav
  • wma
  • wmv
  • xls

  SOLUTION

Minimum Scan Engine:

9.700

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

Identify and terminate files detected as TROJ_CRYPCTB.JK

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. 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.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

Search and delete these files

[ Learn More ]
There may be some component 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 Temp%\{original file name}.rtf
%User Temp%\{random}.{extension}

Step 4

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


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