RANSOM_CRYPWALL.RUI

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 deletes the initially executed copy of itself.

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.)

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

(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.)

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"

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} = "{RSA PUBLIC KEY} "

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\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 possibly malicious URL:

• http://{BLOCKED}walk.com/cache/ap5.php
• http://{BLOCKED}gasten.com/wp-content/plugins/wp-db-backup-made/ap1.php
• http://{BLOCKED}uli.org/wp-content/plugins/wp-db-backup-made/ap2.php
• http://{BLOCKED}music.com/wp-content/plugins/wp-db-backup-made/ap3.php
• http://{BLOCKED}njalidental.com/wp-content/plugins/wp-db-backup-made/ap3.php
• http://{BLOCKED}.gr/wp-content/ap3.php
• http://{BLOCKED}biz/wp-content/plugins/social-locker/panda-items/social-locker/admin/metaboxes/ap4.php
• http://{BLOCKED}rowice.zawiercie.powiat.pl/config/ap1.php
• http://{BLOCKED}ycare.com/wp-content/themes/twentythirteen/ap4.php
• http://{BLOCKED}nhaphat.com/wp-content/plugins/revslider/css/jui/new/images/ap2.php
• http://{BLOCKED}-trans.com/wp-content/plugins/wp-db-backup-made/ap5.php
• http://{BLOCKED}ternetdanang.com/wp-content/plugins/jetpack/modules/widgets/gallery/css/ap4.php
• http://{BLOCKED}psinhvien.net/wp-content/plugins/better-wp-security/modules/free/brute-force/js/ap3.php
• http://{BLOCKED}ellardemo.net/wp-content/plugins/wp-db-backup-made/ap4.php
• http://{BLOCKED}g.com.br/wp-content/ap5.php
• http://{BLOCKED}rucks.com/wp-content/plugins/wpclef/assets/src/sass/bourbon/ap1.php
• http://{BLOCKED}aoibf.com/images/stories/ap1.php
• http://{BLOCKED}atapps.com/wp-content/themes/asteria-lite/redux/assets/css/vendor/ap2.php
• http://{BLOCKED}housheying.com/wp-content/plugins/wp-db-backup-made/ap3.php
• http://{BLOCKED}.net/old/wp-content/plugins/wordbook/facebook-platform/php/jsonwrapper/ap2.php
• http://{BLOCKED}dudak.com/wp-content/themes/imagazine/images/social/3/24/ap5.php
• http://{BLOCKED}rk.com/wp-content/plugins/wp-db-backup-made/ap4.php
• http://{BLOCKED}yllc.com/wp-content/themes/twentytwelve/ap1.php
• http://{BLOCKED}.bg/administrator/components/com_joomlaupdate/ap4.php
• http://{BLOCKED}opping.com/cache/ap2.php
• http://{BLOCKED}e.cat/ap1.php
• http://{BLOCKED}turk.com/wp-content/plugins/wp-db-backup-made/ap5.php

It deletes the initially executed copy of itself

NOTES:

This malware drops HELP_DECRYPT.HTML, HELP_DECRYPT.PNG, HELP_DECRYPT.TXT and HELP_DECRYPT.URL to all folders where files are encrypted. It connects to the following non-malicious URLs:

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