TROJ_CRYPWALL.XT
Ransom:Win32/Crowti.A (Microsoft), Trojan.Win32.CryptoWall.a (v)( Sunbelt), W32/Ngrbot.AERQ!worm (Fortinet), Worm.Win32.Ngrbot.aerq (Kaspersky)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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 itself after execution.
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.
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} = "%System Root%\{random 1}\{random 1}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random 1} = "%Application Data%\{random 1}.exe"
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\{random}\
CRYPTLIST
It adds the following registry entries:
HKEY_CURRENT_USER\Software\{random}\
CRYPTLIST
{path and file name of encrypted file} = "{hex values}"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
DisableSR = "1"
Dropping Routine
This Trojan drops the following files:
- %System Root%\{random 1}\{random 1}.exe
- %Application Data%\{random 1}.exe
- %User Startup%\{random 1}.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
Other Details
This Trojan connects to the following possibly malicious URL:
- {BLOCKED}canajoker.com
- {BLOCKED}dominicana.com
- {BLOCKED}adshowdominicana.com
- {BLOCKED}kanabestplace.com
- {BLOCKED}tdominicana.com
It deletes itself after execution.
NOTES:
It drops the following files in every directory of the affected system:
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.URL
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
Restart in Safe Mode
Step 3
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} = "%System Root%\{random 1}\{random 1}.exe"
- {random} = "%System Root%\{random 1}\{random 1}.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {random 1} = "%Application Data%\{random 1}.exe"
- {random 1} = "%Application Data%\{random 1}.exe"
Step 4
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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
- From: DisableSR = "1"
To: DisableSR = "0"
- From: DisableSR = "1"
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\{random}
- CRYPTLIST
- CRYPTLIST
Step 6
Search and delete these components
- %System Root%\{random 1}\{random 1}.exe
- %Application Data%\{random 1}.exe
- %User Startup%\{random 1}.exe
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.URL
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPWALL.XT. 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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