TROJ_CRYPLOCK.XW

 Analysis by: David John Agni

 ALIASES:

Win32/Filecoder.DI (ESET-NOD32), Ransom:Win32/Teerac (Microsoft), Trojan.Cryptolocker.E (Symantec)

 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, Dropped by other malware

This TorrentLocker variant has the capability to double the amount of decryption after its 5-day deadline. It arrives via spam message purporting as a business email that targeted an Australian company.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

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 connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

423,964 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 Jul 2015

Payload:

Connects to URLs/IPs, Steals information, 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 copies of itself into the affected system:

  • {created folder}\{random folder name}\01000000 - encrypted copy
  • %Windows%\{random 8 letters}.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following file(s)/component(s):

  • {created folder}\{random folder name}\00000000
  • {created folder}\{random folder name}\02000000
  • {created folder}\{random folder name}\03000000 - copy of ransom note
  • {created folder}\{random folder name}\04000000

It adds the following processes:

  • explorer.exe

It creates the following folders:

  • %ProgramData%\{random folder name} - Winodws Vista and Above
  • %All Users Profile%\Application Data\{random folder name} - Windows XP and Below

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.. %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000, XP, and Server 2003, or C:\ProgramData on Windows Vista, 7, and 8. )

It injects codes into the following process(es):

  • created explorer.exe

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\Run
{random 8 letters} = "%Windows%\{random 8 letters}.exe"

Information Theft

This Trojan gathers the following data:

  • Machine GUID
  • Computer name

Other Details

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

  • https://{BLOCKED}on.net/topic.php

It encrypts files with the following extensions:

  • 3ds
  • 3fr
  • 3pr
  • 7z
  • ab4
  • ac2
  • accdb
  • accde
  • accdr
  • accdt
  • acr
  • adb
  • agd1
  • ai
  • ait
  • al
  • apj
  • arw
  • asm
  • asp
  • bak
  • bdb
  • bgt
  • bik
  • bkp
  • blend
  • bpw
  • cdf
  • cdr
  • cdr3
  • cdr4
  • cdr5
  • cdr6
  • cdrw
  • cdx
  • ce1
  • ce2
  • cer
  • cfp
  • cgm
  • cib
  • cls
  • cmt
  • cpi
  • cpp
  • cr2
  • craw
  • crt
  • crw
  • csh
  • csl
  • css
  • csv
  • dac
  • db
  • 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
  • fh
  • fhd
  • fpx
  • fxg
  • gray
  • grey
  • gry
  • hbk
  • hpp
  • ibank
  • awg
  • backup
  • backupdb
  • ibd
  • ibz
  • idx
  • iiq
  • incpas
  • jpeg
  • jpg
  • js
  • kc2
  • kdbx
  • kdc
  • kpdx
  • lua
  • mdb
  • mdc
  • mef
  • mfw
  • mmw
  • moneywell
  • mos
  • mpg
  • mrw
  • myd
  • ndd
  • nef
  • nop
  • nrw
  • ns2
  • ns3
  • ns4
  • nsd
  • nsf
  • nsg
  • nsh
  • nwb
  • 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
  • pl
  • pot
  • potm
  • potx
  • ppam
  • pps
  • ppsm
  • ppsx
  • ppt
  • pptm
  • pptx
  • ps
  • psafe3
  • psd
  • ptx
  • py
  • ra2
  • raf
  • rar
  • raw
  • rdb
  • rtf
  • rw2
  • rwl
  • rwz
  • s3db
  • sas7bdat
  • sav
  • sd0
  • sd1
  • sda
  • sdf
  • sldm
  • sldx
  • sql
  • 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

It renames encrypted files using the following names:

  • {original file name and extension}.encrypted

NOTES:

It drops the ransom note, DECRYPT_INSTRUCTIONS.html to every directory it encrypts.

It deletes shadow copies by executing the following command:

  • vssadmin.exe Delete Shadows /All /Quiet

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

  SOLUTION

Minimum Scan Engine:

9.750

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

Restart in Safe Mode

[ Learn More ]

Step 4

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\Run
    • {random 8 letters} = "%Windows%\{random 8 letters}.exe"

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • {created folder}\{random folder name}

Step 6

Search and delete these files

[ 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.
  • DECRYPT_INSTRUCTIONS.html

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPLOCK.XW. 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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