Analysis by: Jennifer Gumban
ALIASES:

Trojan:Win32/Crilock.A (Microsoft)

 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: Dropped by other malware, 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.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 743,424 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 24 Sep 2013
Payload: Others

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:

  • %User Profile%\Application Data\{Encrypted GUID}.exe (set to hidden)

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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

  • Local\{GUID}
  • Global\{GUID}

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 = %User Profile%\Application Data\{Encrypted GUID}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software
CryptoLocker =

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan encrypts files with the following extensions:

  • .accdb
  • .arw
  • .bay
  • .cdr
  • .cer
  • .crt
  • .crw
  • .dbf
  • .dcr
  • .der
  • .dng
  • .doc
  • .docm
  • .docx
  • .dwg
  • .dxf
  • .dxg
  • .eps
  • .erf
  • .indd
  • .jpe
  • .jpg
  • .kdc
  • .mdb
  • .mdf
  • .mef
  • .mrw
  • .nef
  • .nrw
  • .odb
  • .odc
  • .odm
  • .odp
  • .ods
  • .odt
  • .orf
  • .pdd
  • .pef
  • .pem
  • .pfx
  • .ppt
  • .pptm
  • .pptx
  • .psd
  • .pst
  • .ptx
  • .raf
  • .raw
  • .rtf
  • .rwl
  • .srf
  • .srw
  • .wpd
  • .wps
  • .xlk
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx

It deletes the initially executed copy of itself

NOTES:

This malware tries to connect to following URLs in order to get the key for file encryption.

  • http://{Pseudo-Random Domain}.biz
  • http://{Pseudo-Random Domain}.ru
  • http://{Pseudo-Random Domain}.net
  • http://{Pseudo-Random Domain}.info
  • http://{Pseudo-Random Domain}.co.uk
  • http://{Pseudo-Random Domain}.com
  • http://{Pseudo-Random Domain}.org

It demands users to pay a fine via any of the following payment methods:

  • Bitcoin
  • MoneyPak

It encrypts files using a complex encryption routine. This prevents users from restoring the encrypted files.

It displays the following image containing the ransom message:

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.298.06
FIRST VSAPI PATTERN DATE: 24 Sep 2013
VSAPI OPR PATTERN File: 10.299.00
VSAPI OPR PATTERN Date: 25 Sep 2013

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 = %User Profile%\Application Data\{Encrypted GUID}.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. 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_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.AB. 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 6

Restore a file/s that has/have been corrupted/modified by this malware/grayware

To restore system files:

• For Windows 2000:

  1. Insert your Windows 2000 Installation CD in your CD-ROM drive.
  2. Click Start>Run.
  3. In the Open text box, type the following then click OK:
    expand D:\i386\{file to restore}.ex_ %windir%\system32\{file to restore}.exe

    4. (Note: In the example above, D: refers to the CD-ROM drive. If your CD-ROM drive is not D:, please change the letter accordingly. Also, the file to restore is C:\WINNT\System32\explorer.exe.)

• For Windows XP and Windows Server 2003:

  1. Click Start>Run.
  2. In the Open text box, type the following then click OK:
    MSCONFIG

  3. Make sure that the option Normal startup - load all device drivers and services option is selected.

  4. Click the Expand button.
  5. In the dialog box that appears, type the following:

    6. Wherein:
    • File to restore contains the path and file name of the file you wish to restore.
    • Restore from contains the path to the Windows CAB files. This path may vary from machine to machine. It may be in a local drive, in a network drive, or in a CD-ROM. In the local drive, it is usually in C:\WINDOWS\OPTIONS\INSTALL.
    • Save file in contains the path of the file you wish to restore (Do not include the file name).
  6. Click the Expand button.


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