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TROJ_CRYPFUD.D

April 23, 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:

Downloaded from the Internet, Dropped by other malware

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 drops copies of itself in the Windows Common Startup folder to enable its automatic execution at every system startup.

It modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

410,356 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

21 Apr 2015

Payload:

Encrypts files, Connects to URLs/IPs, 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 files:

  • %Application Data%\sign.bmp
  • %Start Menu%\Programs\Startup\sign.bmp

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.. %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu 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 drops the following copies of itself into the affected system:

  • %Application Data%\{original filename}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.)

Autostart Technique

This Trojan drops copies of itself in the Windows Common Startup folder to enable its automatic execution at every system startup.

Other System Modifications

This Trojan sets the system's desktop wallpaper to the following image:

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{BLOCKED}truments.co.uk/script.php
  • http://{BLOCKED}truments.co.uk/cgi-bin/script.php

It encrypts files with the following extensions:

  • 113
  • 1cd
  • 3gp
  • 73b
  • 7z
  • a3d
  • abf
  • abk
  • accdb
  • arj
  • as4
  • asm
  • asvx
  • ate
  • avi
  • bac
  • bak
  • bck
  • bkf
  • cdr
  • cer
  • cf
  • cpt
  • csv
  • db3
  • dbf
  • doc
  • docx
  • dt
  • dwg
  • erf
  • fbf
  • fbk
  • fbw
  • fbx
  • fdb
  • gbk
  • gho
  • gzip
  • iv2i
  • jpeg
  • jpg
  • key
  • keystore
  • ldf
  • m2v
  • m3d
  • max
  • mdb
  • mkv
  • mov
  • mpeg
  • nbd
  • nrw
  • nx1
  • odb
  • odc
  • odp
  • ods
  • odt
  • old
  • orf
  • p12
  • pdf
  • pef
  • ppsx
  • ppt
  • pptm
  • pptx
  • pst
  • ptx
  • pwm
  • pz3
  • qic
  • r3d
  • rar
  • raw
  • rtf
  • rwl
  • rx2
  • sbs
  • sldasm
  • sldprt
  • sn1
  • sna
  • spf
  • sr2
  • srf
  • srw
  • tbl
  • tib
  • tis
  • txt
  • wab
  • wps
  • x3f
  • xls
  • xlsb
  • xlsk
  • xlsm
  • xlsx
  • zip

It renames encrypted files using the following names:

  • {original file name and extension}.id-{id}_fudx@inbox.com

However, as of this writing, the said sites are inaccessible.

NOTES:
It looks at drives C: to Z: to encrypt files. It avoids encrypting files located in the following folders:

  • Program Data
  • Program Files
  • Program Files (x86)
  • System Volume Information
  • Temp
  • Windows

  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

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

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.  
  • %Application Data%\fud.bmp
  • %Start Menu%\Programs\Startup\fud.bmp

Step 4

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

Reset Internet security settings

[ Learn More ]

NOTES:
Restore the encrypted files by this malware from backup. Note that the encrypted files have the extension .id-{id}_fudx@inbox.com.


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