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TROJ_CRILOCK.AY

November 18, 2013
 Analysis by: Sabrina Lei Sioting
 ALIASES:

Trojan.Win32.Crilock (Ikarus), Trojan.Win32.Menti.qtml (Kaspersky), Ransom-O (McAfee) Trojan:Win32/Crilock.B (Microsoft), Mal/Ransom-BZ (Sophos),

 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: No

  • 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 modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size:

859,648 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

12 Nov 2013

Payload:

Connects to URLs/IPs, 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 and executes them:

  • %Application Data%\{random}.exe

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

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

  • Global\{random letters}
  • Local\{random letters}

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}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*CryptoLocker = "%Application Data%\{random}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\CryptoLocker_{4-digit number}

HKEY_CURRENT_USER\Software\CryptoLocker_{4-digit number}\
Files

It adds the following registry entries:

HKEY_CURRENT_USER\Software\CryptoLocker_{4-digit number}
PublicKey = “{random values}"

HKEY_CURRENT_USER\Software\CryptoLocker_{4-digit number}\
Files
{path and file name of encrypted file} = “{hex value}”

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

NOTES:

It 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
  • .com
  • .info
  • .net
  • .org
  • .ru

It encrypts files with the following extensions:

  • *.3fr
  • *.3gp
  • *.accdb
  • *.arw
  • *.bay
  • *.cdr
  • *.cer
  • *.cr2
  • *.crt
  • *.crw
  • *.dbf
  • *.dcr
  • *.der
  • *.dng
  • *.doc
  • *.docm
  • *.docx
  • *.dwg
  • *.dxf
  • *.dxg
  • *.eps
  • *.erf
  • *.indd
  • *.jpe
  • *.jpg
  • *.kdc
  • *.m4v
  • *.mdb
  • *.mdf
  • *.mef
  • *.mov
  • *.mp4
  • *.mrw
  • *.nef
  • *.nrw
  • *.odb
  • *.odc
  • *.odm
  • *.odp
  • *.ods
  • *.odt
  • *.orf
  • *.p12
  • *.p7b
  • *.p7c
  • *.pdd
  • *.pdf
  • *.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

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.408.01

FIRST VSAPI PATTERN DATE:

12 Nov 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 = "%Application Data%\{random}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *CryptoLocker = "%Application Data%\{random}.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_{4-digit number}

Step 5

Reset Internet security settings

[ Learn More ]

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRILOCK.AY. 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 7

Restore deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.


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