RANSOM_CRYPWALL.CL
Trojan.Cryptodefense (Symantec), Ransom:Win32/Crowti (Microsoft), Trojan.Win32.Yakes.mxrl (Kaspersky)
Windows
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.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
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:
- %User Startup%\HELP_DECRYPT.HTML
- %User Startup%\HELP_DECRYPT.PNG
- %User Startup%\HELP_DECRYPT.TXT
- %User Startup%\HELP_DECRYPT.URL
(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.)
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.)
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
It connects to the following possibly malicious URL:
- {BLOCKED}icequine.org.nz/wp-content/themes/poloraytheme/functions/HdIC_W.php?{random letter}={ransom values}
- {BLOCKED}e.biz/wp-content/plugins/max-banner-ads-pro/5Yfhdr.php?{random letter}={ransom values}
- {BLOCKED}v.com.tr/wp-content/plugins/newsletter/4dMplH.php?{random letter}={ransom values}
- {BLOCKED}yourtown.info/wp-content/themes/toommoreltheme/_pH5Ck.php?{random letter}={ransom values}
- {BLOCKED}y/wp-content/plugins/akismet/4BWtIF.php?{random letter}={ransom values}
- {BLOCKED}y/wp-content/plugins/akismet/O_xjRv.php?{random letter}={ransom values}
- {BLOCKED}ygulamaoteli.com/wp-content/themes/welcome_inn-parent/framework/extensions/contactform/static/VNtDfl.php?{random letter}={ransom values}
- {BLOCKED}monte.ua/wp-content/plugins/cherry-plugin/D3sOjY.php?{random letter}={ransom values}
- {BLOCKED}monte.ua/wp-content/plugins/cherry-plugin/PLlfEN.php?{random letter}={ransom values}
- {BLOCKED}trailer.us/wp-content/plugins/advanced-excerpt/1VtP3W.php?{random letter}={ransom values}
- {BLOCKED}models.ru/tmp/install_534f08d496bdb/tinymce/js/tinymce/plugins/bbcode/GAwCYO.php?{random letter}={ransom values}
- {BLOCKED}a.ru/wp-content/themes/dk/Sp6u0B.php?{random letter}={ransom values}
- {BLOCKED}osim.ro/wp-content/plugins/contact-form-7/CwR04H.php?{random letter}={ransom values}
- {BLOCKED}ddeli.com/media/editors/tinymce/jscripts/tiny_mce/plugins/paste/GbWzVt.php?{random letter}={ransom values}
- {BLOCKED}sti.ro/wp-content/plugins/navayan-subscribe/SYbJT9.php?{random letter}={ransom values}
- {BLOCKED}elacasse.ca/wp-content/plugins/symple-shortcodes/EmATUG.php?{random letter}={ransom values}
- {BLOCKED}oto.ru/wp-content/themes/Velluce/IzOSnD.php?{random letter}={ransom values}
- {BLOCKED}sult.by/wp-content/plugins/all-in-one-seo-pack/JqT9Ls.php?{random letter}={ransom values}
- {BLOCKED}vografico.es/wp-content/themes/book-store backup/BhRfIp.php?{random letter}={ransom values}
- {BLOCKED}unitycup.com/media/editors/tinymce/jscripts/tiny_mce/plugins/contextmenu/InyfWv.php?{random letter}={ransom values}
- {BLOCKED}edpetsgroomingacademy.co.uk/wp-content/plugins/slideshow-jquery-image-gallery/7sinRu.php?{random letter}={ransom values}
- {BLOCKED}.ru/wp-content/themes/twentytwelve/6x_nV5.php?{random letter}={ransom values}
- {BLOCKED}.ru/wp-content/themes/twentytwelve/uQYbdq.php?{random letter}={ransom values}
- {BLOCKED}vefxstudio.co.uk/wp-content/themes/spacious/DiJv3L.php?{random letter}={ransom values}
- {BLOCKED}tprovider.nl/wp-content/uploads/genesis-extender/plugin/images/HaryfG.php?{random letter}={ransom values}
- {BLOCKED}s/wp-content/themes/twentyfifteen/Bamzho.php?{random letter}={ransom values}
- {BLOCKED}znesa.ru/wp-content/plugins/tw-recent-posts-widget/d30UGa.php?{random letter}={ransom values}
- {BLOCKED}znesa.ru/wp-content/plugins/tw-recent-posts-widget/ILEKUM.php?{random letter}={ransom values}
- {BLOCKED}edia.com/wp-content/uploads/2015/09/9rjMyJ.php?{random letter}={ransom values}
- {BLOCKED}re-select.nl/wp-content/themes/genesis/qMfFUp.php?{random letter}={ransom values}
- {BLOCKED}rbrendan.biz/wp-content/themes/twentyfifteen/pLXtNm.php?{random letter}={ransom values}
- {BLOCKED}rbrendan.info/wp-content/themes/genesis/t58Esq.php?{random letter}={ransom values}
- {BLOCKED}rbrendan.me/wp-content/themes/twentyfourteen/pYE7yW.php?{random letter}={ransom values}
- {BLOCKED}rbrendan.mobi/wp-content/plugins/contact-form-7/t1TrNk.php?{random letter}={ransom values}
- {BLOCKED}rbrendan.us/wp-content/plugins/wordpress-importer/NyUkLc.php?{random letter}={ransom values}
- {BLOCKED}auckeg1db2a.xn--p1ai/wp-content/plugins/shortcodes-ultimate/hntNzB.php?{random letter}={ransom values}
- {BLOCKED}u/wp-content/plugins/wp-lightbox-2/107iNE.php?{random letter}={ransom values}
It does the following:
- Capable of encrypting files in the affected system
- Drops HELP_DECRYPT.HTML, HELP_DECRYPT.PNG, HELP_DECRYPT.TXT, and HELP_DECRYPT.URL to the folders where the files are encrypted
It deletes the initially executed copy of itself
SOLUTION
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
Step 4
Delete this registry value
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"
- {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"
- {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)
- *{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)
- *{random 7 characters} = "%Application Data%\{random 8 characters}.exe" (for Windows Vista and above only)
Step 5
Delete this registry key
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}
- {UID}
Step 6
Restore these modified registry values
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\SYSTEM\CurrentControlSet\Services\ERSvc
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
- From: DisableSR = "1"
To: DisableSR = "0"
- From: DisableSR = "1"
Step 7
Search and delete this file
- 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.CL. 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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