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TROJ_CRILOCK.AF

September 25, 2017
 Analysis by: Anthony Joe Melgarejo
 ALIASES:

Trojan:Win32/Crilock.B (Microsoft), Trojan.Ransomcrypt.F (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 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:

766,976 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Oct 2013

Payload:

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 copies of itself into the affected system and executes them:

  • %Application Data%\{random file name}.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.)

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

  • {random string 1}
  • {random string 2}

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
CryptoLocker = "%Application Data%\{random file name}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\CryptoLocker

HKEY_CURRENT_USER\Software\CryptoLocker\
Files

It adds the following registry entries:

HKEY_CURRENT_USER\Software\CryptoLocker
PublicKey = “{random values}"

HKEY_CURRENT_USER\Software\CryptoLocker\
Files
{path and file name of encrypted file} = “{hex value}”

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\ CryptoLocker

HKEY_CURRENT_USER\Software\CryptoLocker\
Files

NOTES:

This Trojan attempts to download the key to be used in encrypting files by connecting to random generated domains with the following extensions:

  • biz/home
  • co.uk/home
  • com/home
  • info/home
  • net/home
  • org/home
  • ru/home
It encrypts files with the following extensions:
  • *.3fr
  • *.accdb
  • *.arw
  • *.bay
  • *.cdr
  • *.cer
  • *.cr2
  • *.crt
  • *.crw
  • *.dbf
  • *.dcr
  • *.der
  • *.dng
  • *.doc
  • *.docm
  • *.docx
  • *.dwg
  • *.dxf
  • *.dxg
  • *.eps
  • *.erf
  • *.indd
  • *.kdc
  • *.mdb
  • *.mdf
  • *.mef
  • *.mrw
  • *.nef
  • *.nrw
  • *.odb
  • *.odc
  • *.odm
  • *.odp
  • *.ods
  • *.odt
  • *.orf
  • *.p12
  • *.p7b
  • *.p7c
  • *.pdd
  • *.pef
  • *.pem
  • *.pfx
  • *.ppt
  • *.pptm
  • *.pptx
  • *.psd
  • *.pst
  • *.ptx
  • *.r3d
  • *.raf
  • *.raw
  • *.rtf
  • *.rw2
  • *.rwl
  • *.sr2
  • *.srf
  • *.srw
  • *.wb2
  • *.wpd
  • *.wps
  • *.x3f
  • *.xlk
  • *.xls
  • *.xlsb
  • *.xlsm
  • *.xlsx
It demands users to pay a fine via any of the following payment methods:
  • Bitcoin
  • cashU
  • MoneyPak
  • Ukash

It displays the following ransom message:

It changes the desktop wallpaper to the following:

  SOLUTION

Minimum Scan Engine:

9.300

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

Restart in Safe Mode

[ Learn More ]

Step 3

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
    • CryptoLocker = "%Application Data%\{random file name}.exe"

Step 4

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.

  • In HKEY_CURRENT_USER\Software
    • CryptoLocker

Step 5

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