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RANSOM_CRYPWALL.D

November 30, 2015
 Analysis by: Pearl Charlaine Espejo
 ALIASES:

Ransom:Win32/Crowti!rfn (Microsoft); Trojan.Cryptodefense (Symantec); Trojan horse FileCryptor.EYT (AVG)

 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 the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

264,995 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

18 Nov 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 characters}\{random 8 characters}.exe
  • %Application Data%\{random 8 characters}.exe
  • %User Startup%\{random 8 characters}.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.. %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.)

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 characters}\{random 8 characters}.exe"

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

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

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\{UID}

It modifies the following registry entries:

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\wscsvc
Start = "4"

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

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\wuauserv
Start = "4"

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

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
  • http://curlmyip.com

It connects to the following possibly malicious URL:

  • http://{BLOCKED}gov.br/cpi/telefonia/wp-content/themes/cpi/GcnPfu.php?{random letter}={random values}
  • http://{BLOCKED}.ac.id/wp-content/uploads/iMhCqK.php?{random letter}={random values}
  • http://{BLOCKED}gnok.com/tmp/XmUk10.php?{random letter}={random values}
  • http://{BLOCKED}ee.net/wp-content/uploads/2015/01/EqTf2Q.php?{random letter}={random values}
  • http://{BLOCKED}eg.com/modules/mod_msn/juZPUi.php?{random letter}={random values}
  • http://{BLOCKED}gcom.ucv.cl/wp-content/gallery/nSN1_Z.php?{random letter}={random values}
  • http://{BLOCKED}ite.it/wp-content/themes/lightweight/Y7rNkE.php?{random letter}={random values}
  • http://{BLOCKED}.itu.edu.tr/wp/wp-content/plugins/wp-db-backup/94dXi5.php?{random letter}={random values}
  • http://{BLOCKED}woodenwindows.com/tmp/JFwXS6.php?{random letter}={random values}
  • http://{BLOCKED}donovaly.sk/wp-content/plugins/wp_module/OdZhrT.php?{random letter}={random values}
  • http://{BLOCKED}oy.com/wp-content/plugins/wp-db-backup-made/BYA4Ks.php?{random letter}={random values}
  • http://{BLOCKED}cc/wp-content/themes/twentytwelve/vnUN8e.php?{random letter}={random values}
  • http://{BLOCKED}.com/wp-content/plugins/wp_module/sbML0j.php?{random letter}={random values}
  • http://{BLOCKED}torenonderzoek.nl/wp-content/plugins/wp-db-backup-made/Xoeyqs.php?{random letter}={random values}
  • http://{BLOCKED}pl/stara-strona-backup-20-08-2012/var/j4m502.php?{random letter}={random values}
  • http://{BLOCKED}pl/stara-strona-backup-20-08-2012/var/Srz7Vd.php?{random letter}={random values}
  • http://{BLOCKED}ac.it/wp-content/themes/twentyten/kPog6K.php?{random letter}={random values}
  • http://{BLOCKED}net/wp-content/themes/twentytwelve/H_S2xs.php?{random letter}={random values}
  • http://{BLOCKED}n.com/wp-content/plugins/wp-db-backup/h1X6p7.php?{random letter}={random values}
  • http://{BLOCKED}gsonthefrenchriviera.com/wp-content/uploads/bcswkG.php?{random letter}={random values}
  • http://{BLOCKED}ams.pl/error/403.html
  • http://{BLOCKED}nihayatintadi.com/error404.html
  • http://{BLOCKED}zl.com/wp-content/themes/zsqx/iRWgt3.php?{random letter}={random values}
  • http://{BLOCKED}yatintadi.com/wp-content/plugins/wp-db-backup-made/0Kyc7k.php?{random letter}={random values}
  • http://{BLOCKED}.com/wp-content/plugins/wp-db-backup-made/ZdOaXp.php?{random letter}={random values}
  • http://{BLOCKED}sterplus.ru/wp-content/themes/storefront-paper/WIhbkO.php?{random letter}={random values}
  • http://{BLOCKED}n.com/wp-content/plugins/wp-db-backup1/BDEOY6.php?{random letter}={random values}

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

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.182.05

FIRST VSAPI PATTERN DATE:

30 Nov 2015

VSAPI OPR PATTERN File:

12.183.00

VSAPI OPR PATTERN Date:

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

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 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

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