WORM_CRILOCK.A

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.

Arrival Details

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.

Installation

This worm drops the following copies of itself into the affected system and executes them:

• %System%\msunet.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
MSUpdate = "%System%\msunet.exe"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*MSUpdate = "%System%\msunet.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MSUpdate = "%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\Winlogon
Userinit = "%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:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer
NoDriveTypeAutoRun = "91"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer
NoDriveAutoRun = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoDriveAutoRun = "0"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

• {Removable Drive Letter}:\setup.exe
• {Removable Drive Letter}:\{Filename}.exe - if executable files exist

NOTES:

It connects to the following IP address to download the key used in encrypting the files:

• http://{BLOCKED}morej.{BLOCKED}st3.com/dd/testcon.php
• http://{BLOCKED}.{BLOCKED}.56.1/dd/testcon.php
• http://{BLOCKED}morej.{BLOCKED}ge.biz/ee/testcon.php

It encrypts files with the following extensions:

• *.3fr
• *.accdb
• *.ai
• *.arw
• *.bay
• *.cdr
• *.cer
• *.cr2
• *.crt
• *.crw
• *.dbf
• *.dcr
• *.der
• *.dng
• *.doc
• *.docm
• *.docx
• *.dwg
• *.dxf
• *.dxg
• *.eps
• *.erf
• *.indd
• *.jpe
• *.jpg
• *.kdc
• *.mdb
• *.mdf
• *.mef
• *.mp3
• *.mp4
• *.mrw
• *.nef
• *.nrw
• *.odb
• *.odm
• *.odp
• *.ods
• *.odt
• *.orf
• *.p12
• *.p7b
• *.p7c
• *.pdd
• *.pef
• *.pem
• *.pfx
• *.ppt
• *.pptm
• *.pptx
• *.psd
• *.pst
• *.ptx
• *.r3d
• *.raf
• *.raw
• *.rtf
• *.rwl
• *.srf
• *.srw
• *.txt
• *.wb2
• *.wpd
• *.wps
• *.xlk
• *.xls
• *.xlsb
• *.xlsm
• *.xlsx

It demands users to pay a fine via any of the following payment methods:

• Bitcoin

It mimics activators for the following software:

• Adobe Photoshop
• ESET
• Office 2013
• Team Viewer
• Windows

It deletes all .EXE files found on removable drives and replace it with its copy using the names of the existing .EXE files.