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This is a Cryptolocker variant that has propagation routines, enabling it to easily spread to other systems. The said routine is important since other CRILOCK variants do not exhibit the same behavior.
To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.
This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
This worm arrives via removable drives.
It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
This worm drops the following copies of itself into the affected system and executes them:
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunMSUpdate = "%System%\msunet.exe"
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce*MSUpdate = "%System%\msunet.exe"
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunMSUpdate = "%System%\msunet.exe"
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce*MSUpdate = "%System%\msunet.exe"
It modifies the following entry(ies) to allow itself to run on safe mode:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\WinlogonUserinit = "%System%\userinit.exe, %System%\msunet.exe"
(Note: The default value data of the said registry entry is %System%\userinit.exe.)
Other System Modifications
This worm adds the following registry keys:
It adds the following registry entries:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\ExplorerNoDriveTypeAutoRun = "91"
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\ExplorerNoDriveAutoRun = "0"
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\ExplorerNoDriveAutoRun = "0"
This worm drops the following copy(ies) of itself in all removable drives:
It connects to the following IP address to download the key used in encrypting the files:
It encrypts files with the following extensions:
It demands users to pay a fine via any of the following payment methods:
It mimics activators for the following software:
It deletes all .EXE files found on removable drives and replace it with its copy using the names of the existing .EXE files.
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Restart in Safe Mode
To restart in Safe Mode:
• For Windows 2000 users
• For Windows XP users
• For Windows Server 2003 users
• For Windows Vista and Windows 7 users
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.
To delete registry keys this malware/grayware created:
Delete this registry value
To delete the registry value this malware/grayware created:
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_CRILOCK.A. 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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