Analysis by: John Kevin Sanchez
ALIASES:

Ransom:Win32/Crowti.A (Microsoft), Trojan-Ransom.CryptoWall3 (Ikarus), Trojan-Ransom.Win32.Cryptodef.wgu (Kaspersky)

 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.

However, as of this writing, the said sites are inaccessible. It deletes itself after execution. It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size: 221,184 bytes
File Type: , EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Jul 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 drops the following copies of itself into the affected system:

  • %System Root%\{random 8 character filename}\{random 8 character filename}.exe
  • %Application Data%\{random 8 character filename}.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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 drops the following files:

  • %Desktop%\HELP_DECRYPT.HTML
  • %Desktop%\HELP_DECRYPT.PNG
  • %Desktop%\HELP_DECRYPT.TXT
  • %Desktop%\HELP_DECRYPT.URL
  • %User Startup%\HELP_DECRYPT.HTML
  • %User Startup%\HELP_DECRYPT.PNG
  • %User Startup%\HELP_DECRYPT.TXT
  • %User Startup%\HELP_DECRYPT.URL
  • {folders containing encrypted files}\HELP_DECRYPT.TXT
  • {folders containing encrypted files}\HELP_DECRYPT.HTML
  • {folders containing encrypted files}\HELP_DECRYPT.URL
  • {folders containing encrypted files}\HELP_DECRYPT.PNG

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.. %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

It adds the following processes:

  • explorer.exe
  • svchost.exe

It creates the following folders:

  • %System Root%\{random 8 character filename}

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

It is injected into the following processes running in memory:

  • created explorer.exe
  • created svchost.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 7 characters} = %System Root%\{random 8 character filename}\{random 8 character filename}.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random 8 character filename} = %Application Data%\{random 8 character filename}.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{random 6 characters} = %System Root%\{random 8 character filename}\{random 8 character filename}.exe (for Windows Vista and above)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{random 7 characters} = %Application Data%\{random 8 character filename}.exe (for Windows Vista and above)

It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{random 8 character filename}.exe - copy of itself

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\{UID}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\{UID}
{random 2 characters} = "{contents of HELP_DECRYPT.TXT}"

HKEY_CURRENT_USER\Software\{UID}
{random 2 characters} = "{contents of HELP_DECRYPT.HTML}"

HKEY_CURRENT_USER\Software\{UID}
{random 2 characters} = "{contents of HELP_DECRYPT.URL}"

HKEY_CURRENT_USER\Software\{UID}\
{random key}
{Path and file of encrypted file} = "{hex values}"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
DisableSR = 1

(Note: The default value data of the said registry entry is 0.)

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

  • http://ip-addr.es
  • http://myexternalip.com/raw

It connects to the following possibly malicious URL:

  • http://{BLOCKED}ion.co.uk/wp-content/uploads/2015/03/update-a9afa977161aa75fe3a7b760b1051876/tmp/ee.php
  • http://{BLOCKED}uresandtrips.com/wp-content/plugins/cc.php
  • http://{BLOCKED}uadalajara.org/wp-content/plugins/dd.php
  • http://{BLOCKED}-central.de/piwik/core/Tracker/Db/Pdo/dd.php
  • http://{BLOCKED}viciossas.net/wp-includes/cc.php
  • http://blog.{BLOCKED}iprzyszlosc.pl/wp-includes/js/tinymce/plugins/cc.php
  • http://{BLOCKED}nmasonry.com/wp-includes/aa.php
  • http://{BLOCKED}nc.com/wp-content/plugins/bb.php
  • http://{BLOCKED}as.net/wp-content/plugins/bb.php
  • http://freetrial.{BLOCKED}nline.com/wp-content/plugins/bb.php
  • http://{BLOCKED}xp.com/starcraft2guides/wp-content/plugins/aa.php
  • http://{BLOCKED}atone.com/wp-content/plugins/aa.php
  • http://{BLOCKED}4.com/news3/wp-includes/bb.php
  • http://{BLOCKED}illiams.com.au/wp-content/cc.php
  • http://{BLOCKED}potolkov12.ru/wp-content/plugins/cc.php
  • http://{BLOCKED}-healthcare-management-for-leaders.com/bemerkenswert/wp-content/ee.php
  • http://{BLOCKED}estorationpros.com/wp-content/plugins/ee.php
  • http://{BLOCKED}u.co.uk/wp-includes/dd.php
  • http://{BLOCKED}c.co.za/cc.php
  • http://{BLOCKED}healthinternational.com/sgsbeautify.com/wp-content/bb.php
  • http://{BLOCKED}rsscandal.com/wp-content/themes/cc.php
  • http://{BLOCKED}a-biografikwn.com/wp-content/plugins/bb.php
  • http://pulse.{BLOCKED}z.com/wp-content/uploads/updatedmaps/Arvada/Old%20Arvada/bb.php
  • http://{BLOCKED}smilesofhamden.com/wp-content/aa.php
  • http://{BLOCKED}lesschoolcentral.org/dir/wp-content/ee.php
  • http://{BLOCKED}-jones.co.nz/wp-includes/js/tinymce/plugins/aa.php
  • http://{BLOCKED}form.com.sg/staging/wp-includes/aa.php
  • http://{BLOCKED}immer.nl/wp-content/themes/dd.php
  • http://{BLOCKED}girlphotography.com/wp-includes/ee.php
  • http://{BLOCKED}redservices.org.uk/wp-content/plugins/dd.php
  • http://www.{BLOCKED}anty.com/wp-content/themes/dd.php
  • http://{BLOCKED}og.co.za/aa.php
  • http://{BLOCKED}o.com/wp-content/plugins/woocommerce-one-click/vendor/stripe/stripe-php/lib/Error/ee.php
  • http://{BLOCKED}hsolutions.com/wp-includes/js/tinymce/themes/advanced/skins/o2k7/img/dd.php

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

It deletes itself after execution.

It is capable of encrypting files in the affected system.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.814.05
FIRST VSAPI PATTERN DATE: 03 Oct 2016
VSAPI OPR PATTERN File: 12.815.00
VSAPI OPR PATTERN Date: 04 Oct 2016

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 these registry values

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random 7 characters} = %System Root%\{random 8 character filename}\{random 8 character filename}.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random 8 character filename} = %Application Data%\{random 8 character filename}.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *{random 6 characters} = %System Root%\{random 8 character filename}\{random 8 character filename}.exe (for Windows Vista and above)
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *{random 7 characters} = %Application Data%\{random 8 character filename}.exe (for Windows Vista and above)

Step 5

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
    • {UID}

Step 6

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
    • From: DisableSR = "1"
      To: DisableSR = 0

Step 7

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.
  • HELP_DECRYPT.HTML
  • HELP_DECRYPT.PNG
  • HELP_DECRYPT.TXT
  • HELP_DECRYPT.URL

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPWALL.JKS. 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 9

Restore encrypted files from backup.


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