RANSOM_CRYPWALL.XXTYG

September 08, 2015
 Analysis by: Homer Pacag
 ALIASES:

Trojan.Cryptodefense (Symantec);VirTool:Win32/Injector (Microsoft)

 PLATFORM:

Windows

 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 modifies registry entries to disable various system services. This action prevents most of the system functions to be used.

It connects to certain websites to send and receive information. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

182,272 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

06 Aug 2015

Payload:

Connects to URLs/IPs, Encrypts files

Installation

This Trojan drops the following copies of itself into the affected system:

  • %System Root%\{random 8 characters}\{random 8 characters}.dll
  • %Application Data%\{random 8 characters}.dll

(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 and executes the following files:

  • %Desktop%\HELP_DECRYPT.HTML
  • %Desktop%\HELP_DECRYPT.PNG
  • %Desktop%\HELP_DECRYPT.TXT
  • %Desktop%\HELP_DECRYPT.URL

(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.)

It adds the following processes:

  • explorer.exe
  • svchost.exe

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:

HKCU\Software\Microsoft\
Windows\CurrentVersion\Run
{random 7 characters} = %System%\regsvr32.exe %System Root%\{random 8 characters}\{random 8 characters}.dll

HKCU\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{random 7 characters} = %System%\regsvr32.exe %System Root%\{random 8 characters}\{random 8 characters}.dll

HKCU\Software\Microsoft\
Windows\CurrentVersion\Run
{random 7 characters} = %System%\regsvr32.exe %Application Data%\{random 8 characters}.dll

HKCU\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{random 7 characters} = %System%\regsvr32.exe %Application Data%\{random 8 characters}.dll

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\{UID}

HKEY_CURRENT_USER\Software\{UID}\
{random key}

It adds the following registry entries:

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

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} = "{RSA PUBLIC KEY}"

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.)

It modifies registry entries to disable the following system services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

(Note: The default value data of the said registry entry is 2.)

Other Details

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

  • http://ip-addr.es

It connects to the following website to send and receive information:

  • {BLOCKED}la.kz/wp-content/plugins/wp-db-backup-made/a.php
  • {BLOCKED}lander.com/wp-content/plugins/wp-db-backup-made/b.php
  • {BLOCKED}digital.com/wp-content/themes/twentytwelve/c.php
  • {BLOCKED}r100unity.com/wp-includes/js/tinymce/skins/wordpress/images/e.php
  • {BLOCKED}v.com/plugins/system/plg_system_rewrite/a.php
  • {BLOCKED}veloper.com/tmp/b.php
  • {BLOCKED}eebangalore.org/wp-content/themes/twentyeleven/d.php
  • {BLOCKED}sscod.com/tmp/e.php
  • {BLOCKED}nadvances.com/wp-content/plugins/updraftplus/oc/guzzle/Guzzle/Service/Command/LocationVisitor/Request/a.php
  • {BLOCKED}urgical.com/plugins/system/plg_system_rewrite/b.php
  • {BLOCKED}orymexico.com/foro/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Storage/Handler/c.php
  • {BLOCKED}mebetterwe.com/wp-content/plugins/wp-antibot-standart/d.php
  • {BLOCKED}acelets.ro/wp-content/themes/twentytwelve/e.php
  • {BLOCKED}kaonline.com/plugins/system/plg_system_rewrite/a.php
  • {BLOCKED}l.vn/wp-content/themes/twentytwelve/b.php
  • {BLOCKED}yroseville.org/wp-content/plugins/wp-antibot-standart/c.php
  • {BLOCKED}rie.de/wp-content/plugins/revslider/css/jui/new/images/d.php
  • {BLOCKED}gc.com.pk/wp-content/plugins/wp-antibot-standart/e.php
  • {BLOCKED}o.de/plugins/system/plg_system_rewrite/a.php
  • {BLOCKED}cement.com/blog/wp-content/plugins/wp-antibot-standart3/b.php
  • {BLOCKED}oftball.com/wp-content/themes/sports-team-theme/includes/advanced-custom-fields/assets/inc/datepicker/images/c.php
  • {BLOCKED}ervisi.info.tr/wp-content/themes/twentytwelve/d.php
  • {BLOCKED}k.info/wp-content/uploads/e.php
  • {BLOCKED}nce.ru/wp-content/themes/dreamynight-10/a.php
  • {BLOCKED}nbahadi.com/wp-content/uploads/b.php
  • {BLOCKED}alemaneslabardena.com/plugins/system/plg_system_rewrite/c.php
  • {BLOCKED}yzworld.com/wp-content/plugins/wp-antibot-standart/d.php
  • {BLOCKED}hop4men.com.br/wp-content/plugins/wp-antibot-standart/a.php
  • {BLOCKED}lhomesearch.com/wp-content/plugins/wp-antibot-standart/b.php
  • {BLOCKED}ic.ro/wp-content/themes/twentytwelve/c.php
  • {BLOCKED}lserwa.com/wp-content/plugins/wp-db-backup-made/a.php
  • {BLOCKED}b.es/wordpress/wp-content/plugins/wp-db-backup-made1/d.php
  • {BLOCKED}welry.com/il/wp-content/plugins/ninja-forms/includes/admin/pages/ninja-forms-settings/tabs/c.php
  • {BLOCKED}a.com/blog/wp-content/plugins/scribe/lib/history/views/meta-box/c.php
  • {BLOCKED}n.ru/wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/nextgen_gallery_display/templates/list/a.php
  • {BLOCKED}n.com/wp-content/themes/twentythirteen/e.php
  • {BLOCKED}nes.com/wp-content/themes/twentyeleven/a.php
  • {BLOCKED}apartman.hu/de/wp-content/plugins/wp-db-backup-made/e.php
  • {BLOCKED}deoyunlari.org/wp-content/themes/twentytwelve/b.php
  • {BLOCKED}imagenes.com/wp-content/plugins/wp-mobile-edition/admin/includes/mobile_themes/mTheme-Unus/images/blue/a.php
  • {BLOCKED}ron.com/wp-content/plugins/contact-form-7/includes/js/jquery-ui/themes/smoothness/images/a.php

It encrypts files with the following extensions:

  • .aif
  • .aifc
  • .aiff
  • .asf
  • .asx
  • .au
  • .bas
  • .bat
  • .bmp
  • .cmd
  • .com
  • .dib
  • .doc
  • .dot
  • .dvr-ms
  • .emf
  • .exe
  • .gif
  • .hta
  • .htm
  • .html
  • .ico
  • .IVF
  • .jfif
  • .jpe
  • .jpeg
  • .jpg
  • .m1v
  • .m3u
  • .mid
  • .midi
  • .mp2
  • .mp2v
  • .mp3
  • .mpa
  • .mpe
  • .mpeg
  • .mpg
  • .mpv2
  • .msi
  • .pdf
  • .pif
  • .png
  • .pot
  • .pot
  • .pps
  • .pps
  • .ppt
  • .reg
  • .rle
  • .rmi
  • .rtf
  • .rtf
  • .scr
  • .snd
  • .tif
  • .tiff
  • .vb
  • .wav
  • .wax
  • .wm
  • .wma
  • .wmf
  • .wmv
  • .wmx
  • .wvx
  • .xls
  • .xlt
  • .xlw
  • .xml
  • .zip

It deletes the initially executed copy of itself

NOTES:

It searches for files to encrypt in all drives except the CD-ROM drive.

It deletes shadow copies by executing the following command:

  • vssadmin.exe Delete Shadows /All /Quiet

It drops and executes HELP_DECRYPT.HTML, HELP_DECRYPT.PNG, HELP_DECRYPT.TXT, and HELP_DECRYPT.URL to the Desktop:

It demands payment for using decryption services:

  SOLUTION

Minimum Scan Engine:

9.750

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random 7 characters} = %System%\regsvr32.exe %System Root%\{random 8 characters}\{random 8 characters}.dll
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {random 7 characters} = %System%\regsvr32.exe %System Root%\{random 8 characters}\{random 8 characters}.dll
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random 7 characters} = %System%\regsvr32.exe %Application Data%\{random 8 characters}.dll
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {random 7 characters} = %System%\regsvr32.exe %Application Data%\{random 8 characters}.dll

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. 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
    • {UID}

Step 6

Restore these modified 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
    • From: DisableSR = "1"
      To: DisableSR = 0
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ERSvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = "4"
      To: Start = 2

Step 7

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.
  • %System Root%\{random 8 characters}\{random 8 characters}.exe
  • %Application Data%\{random 8 characters}.exe
  • %Desktop%\HELP_DECRYPT.TXT
  • %Desktop%\HELP_DECRYPT.PNG
  • %Desktop%\HELP_DECRYPT.URL
  • %Desktop%\HELP_DECRYPT.HTML

Step 8

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