TROJ_CRYPLOCK.KA

 Analysis by: Miguel Carlo Ang

 ALIASES:

a variant of Win32/Injector.BZYZ(ESET-NOD32);Artemis!6E41EDECD54D(McAfee);W32/BZYZ!tr(Fortinet)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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:

242,062 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 May 2015

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 adds the following folders:

  • %All Users Profile%\Application Data\ogewuryhuvosizal

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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 files:

  • %All Users Profile%\Application Data\ogewuryhuvosizal\00000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\01000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\02000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\03000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\04000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\05000000
  • {folder of encrypted file}:\DECRYPT_INSTRUCTIONS.html
  • {folder of encrypted file}:\DECRYPT_INSTRUCTIONS.txt

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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:

  • %Windows%\{8 random characters 1}.exe

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

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{8 random characters 2} = ""%Windows%\{8 random characters 1}.exe""

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\PhishingFilter
EnabledV8 = 0

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\PhishingFilter
EnabledV9 = 0

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\BITS
StateIndex = 0

(Note: The default value data of the said registry entry is 1.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}ar.org:443/topic.php

It encrypts files with the following extensions:

  • {filename}.encrypted

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.654.03

FIRST VSAPI PATTERN DATE:

07 May 2015

VSAPI OPR PATTERN File:

11.655.00

VSAPI OPR PATTERN Date:

08 May 2015

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

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {8 random characters 2} = ""%Windows%\{8 random characters 1}.exe""
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\PhishingFilter
    • EnabledV8 = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\PhishingFilter
    • EnabledV9 = 0

Step 5

Restore this modified 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\BITS
    • StateIndex = 0

Step 6

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.
  • %All Users Profile%\Application Data\ogewuryhuvosizal\00000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\01000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\02000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\03000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\04000000
  • %All Users Profile%\Application Data\ogewuryhuvosizal\05000000
  • {folder name}:\DECRYPT_INSTRUCTIONS.html
  • {folder name}:\DECRYPT_INSTRUCTIONS.txt

Step 7

Search and delete this folder

[ 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.
  • %All Users Profile%\Application Data\ogewuryhuvosizal

Step 8

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